UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl) UvA-DARE (Digital Academic Repository) Towards new measures of inflammation in spondyloarthritis Turina, Maureen Link to publication Citation for published version (APA): Turina, M. C. (2016). Towards new measures of inflammation in spondyloarthritis General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 23 Aug 2018
Transcript
UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl)
UvA-DARE (Digital Academic Repository)
Towards new measures of inflammation in spondyloarthritis
Turina, Maureen
Link to publication
Citation for published version (APA):Turina, M. C. (2016). Towards new measures of inflammation in spondyloarthritis
General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s),other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).
Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, statingyour reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Askthe Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam,The Netherlands. You will be contacted as soon as possible.
Towards new measures of inflammation in spondyloarthritis
Maureen Turina
TOWARDS NEW MEASURES OF
INFLAMMATION IN SPONDYLOARTHRITIS
Maureen Cindy Turina
ISBN: 978-94-6233-234-8Maureen Turina was supported by a fellowship of Janssen. Printing of this thesis was financially supported by ABBVIE B.V., AMC-UvA, the Dutch Arthritis Foundation (het Reumafonds), Janssen-Cilag B.V., Pfizer B.V., and UCB Pharma B.V., which is gratefully acknowledged.
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in anyform or by any means, without permission of the author.
TOWARDS NEW MEASURES OF
INFLAMMATION IN SPONDYLOARTHRITIS
ACADEMISCH PROEFSCHRIFT
ter verkrijging van de graad van doctor
aan de Universiteit van Amsterdam
op gezag van de Rector Magnificus
prof. dr. D.C. van den Boom
ten overstaan van een door het College voor Promoties ingestelde commissie,
in het openbaar te verdedigen in de Agnietenkapel
op vrijdag 1 april 2016, te 12:00 uur
door Maureen Cindy Turina
geboren te Rotterdam
PROMOTIECOMMISSIE:
Promotores: Prof. dr. D.L.P. Baeten Universiteit van AmsterdamProf. dr. R.B.M. Landewé Universiteit van Amsterdam
Overige leden: Prof. dr. D. van Schaardenburg Universiteit van AmsterdamProf. dr. P.I. Spuls Universiteit van AmsterdamProf. dr. G.R.A.M. D’Haens Universiteit van AmsterdamProf. dr. P.L.C.M. van Riel Radboud Universiteit NijmegenDr. F.A. van Gaalen Universiteit Leiden
Faculteit der Geneeskunde
TABLE OF CONTENTS
Chapter 1 General introduction 9
Chapter 2 Serum biomarkers in spondyloarthritis-related diseases: lessons from psoriasis and inflammatory bowel diseases
19
Chapter 3 Serum inflammatory biomarkers fail to identify early axial spondyloartritis: results from the SpondyloArthritis Caught Early (SPACE)-cohort
43
Chapter 4 Clinical and imaging signs of spondyloarthritis in first-degree relatives of HLA-B27 positive ankylosing spondylitis patients: the pre-spondyloarthritis (Pre-SpA) cohort
55
Chapter 5 Calprotectin (S100A8/9) as serum biomarker for clinical response in proof-of-concept trials in axial and peripheral spondyloarthritis
75
Chapter 6 A psychometric analysis of outcome measures in peripheral spondyloarthritis
91
Chapter 7 Calprotectin serum level is an independent marker for radiographic spinal progression in axial spondyloarthritis
107
Chapter 8 General discussion and summary 113
Appendices Nederlandse samenvatting 135Dankwoord 143PhD portfolio 147Curriculum vitae 151List of publications 153
General introduction 1
10 GENERAL INTRODUCTION
SPONDYLOARTHRITIS
Spondyloarthritis (SpA) is a chronic inflammatory disease affecting the axial skeleton, the peripheral joints, and extra-articular organs such as eye, gut, and skin. An important symptom of axial SpA is inflammatory back pain with pain at night and morning stiffness. Spinal inflammation can be accompanied by excessive new bone formation leading to fusion of vertebral bodies and spinal ankylosis. The prototypical and best known form of axial SpA is ankylosing spondylitis (AS). Peripheral SpA may manifest as peripheral arthritis, enthesitis, and/or dactylitis. Peripheral arthritis is characterized by pain, swelling, redness, and stiffness of the joints; the arthritis is mainly of the oligoarticular (1-5 joints) type, with asymmetrical distribution, preferably affecting the large joints of the lower limbs. Peripheral arthritis can be associated with both bone destruction and new bone formation, as described in psoriatic arthritis, being the prototypical form of peripheral SpA. Enthesitis often affects the fascia plantaris and the Achilles tendon. Dactylitis is swelling of an entire digit of the hands (sausage finger) or feet (sausage toe). Extra-articular manifestations include acute anterior uveitis, inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and skin psoriasis. The inflammatory musculoskeletal symptoms of SpA are often effectively treated with nonsteroidal anti-inflammatory drugs (NSAIDs) and, if refractory to NSAIDs, tumor necrosis factor (TNF) inhibitors. TNF inhibitors do inhibit bone destruction in psoriatic arthritis. In contrast, it is still unclear if TNF-inhibitors inhibit new bone formation as seen in both axial and peripheral SpA.
Unmet needs in the management of SpA
Although the management of SpA has improved remarkably in the past years, mainly due to TNF inhibitors, several unmet needs still remain.
A first unmet need is the time required to diagnose SpA. For axial disease, for example, until recently, it took ten years on average from the start of signs and symptoms to diagnose SpA.1,2 This delay has decreased significantly by optimizing the referral strategies from the general practitioner to the rheumatologist,3–5 and by introducing the magnetic resonance imaging (MRI) that is able to depict inflammation of the sacroiliiac joints (SI-joints). Still, however, the average delay between first symptoms and diagnosis of axial SpA remains 5-10 years,6,7 reflecting a long period of uncontrolled signs and symptoms. Comparable data for peripheral SpA are not available. Therefore, we need to study the earlier (yet undiagnosed) phases of clinically established SpA. In addition, the study of the subclinical phases of SpA (i.e. individuals without the symptoms of SpA but already with certain abnormalities specific for SpA (imaging, laboratory tests)) may further help to reduce the unwarranted diagnostic delay. Two main arguments explain why any delay in diagnosing SpA is unwarranted: 1) effective treatment is available to immediately improve signs and symptoms of the disease without further delay,8–14 and 2) treatment during the early phases of the disease may
11
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better halt new bone formation and the progression thereof than late-onset treatment after significant diagnostic delay (window of opportunity in SpA).15–17
A second unmet need is the lack of alternative therapeutic options beyond TNF inhibitors. Despite their major efficacy, TNF inhibitors have several limitations: 1) approximately 40% of the patients do not respond well to TNF inhibitor treatment;8,10–13 2) contra-indications for TNF inhibitors usage and/or side-effects occurring during TNF inhibitor-use limit the clinical potential of this class of treatments; 3) while TNF blockade can halt joint destruction, it likely does not halt new bone formation;15–17 and 4) long-term drug-free remission can still not be achieved.18,19 Clinical studies of novel drugs therefore remain necessary but are rapidly becoming ethically challenging: sufficiently large, long-term placebo controlled trials are ethically disputable in the era of TNF blockade, and difficult to enrol. Therefore, there is a need for alternative strategies to quickly provide go or no-go signals on whether a new drug may show efficacy at the group level in small-scale short-term proof of concept clinical trials (PoCs) before proceeding with larger phase-2b/3 randomized controlled trials.
A third and partially related unmet need is to find valid outcome measures that adequately reflect treatment responses in peripheral disease. In axial SpA, well validated outcome measures such as the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)20 and the Ankylosing Spondylitis Diseases Activity Score (ASDAS)21 exist and are widely used in clinical studies, including therapeutic trials. In peripheral SpA, such outcome measures are lacking, with the exception of psoriatic arthritis: the outcome measures for psoriatic arthritis were either derived from measures originally developed for rheumatoid arthritis (e.g. American College of Rheumatology criteria, ACR) or were newly developed specifically for psoriatic arthritis, including Psoriatic Arthritis Response Criteria (PsARC). In peripheral SpA, Peripheral SpA Response Criteria (PSpARC) is the only set of response criteria developed for peripheral SpA. The discriminatory capacity of these outcome measures has not been properly validated for peripheral SpA. Thus, patient-reported outcome measures or markers determining the efficacy of treatments at the group level are needed in peripheral SpA.
A fourth important unmet need is inhibition of pathological (inappropriate) new bone formation.15–17 New bone formation and the resulting joint ankylosis may impair physical function and thereby quality of life in affected patients. The challenge here is not only to develop novel treatment that, in contrast with current treatments, will halt new bone formation at the group level, but rather to identify those patients that may benefit most of these treatments. Indeed, not all patients with SpA will develop syndesmophytes and ankylosis. Identifying the patients at highest risk of rapid structural progression and treating them accordingly early may be as important to improve outcome in SpA as developing novel treatments.
12 GENERAL INTRODUCTION
Biomarkers
One approach that could help to address the aforementioned challenges is the identification and validation of biomarkers in SpA. A biomarker is defined as a “characteristic that can be objectively measured and evaluated as an indicator of a normal biologic process, a pathophysiologic process, or a pharmacologic response to a therapeutic intervention”.22 A biomarker should ideally be sensitive, specific and reproducible, and obtaining the biomarker should preferably be by a non-invasive procedure. Taking these criteria into account, biomarkers can have an important role in fulfilling the unmet needs in the process of diagnosis, treatment response, and clinical outcome. Examples of valuable biomarkers in other fields are: 1) anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis. This marker is highly specific for diagnosis (specificity of 95%), has good reproducibility, and is easily accessible as it is determined in the serum. Approximately 30% of patients with arthralgia who are ACPA positive will develop RA within one year,23–25 and therefore these antibodies may identify high-risk patients. 2) The human epidermal growth factor receptor 2 (HER2)-status can predict responses to systemic treatment in breast cancer, including trastuzumab (Herceptin®, a monoclonal IgG1 antibody against HER2) or chemotherapeutic agents, including anthracycline- and taxane-containing regimens.26–29 3) CD4+ cell count and viral load in human immunodeficiency virus (HIV), both of which are good prognostic biomarkers which can predict the outcomes such as acquired immune deficiency syndrome (AIDS) and death.30–32
Also in the field of SpA, biomarkers may play an increasingly important role in addressing major clinical challenges such as early diagnosis, prediction and measurement of treatment responses, and prognosis.
AIMS AND OUTLINE OF THIS THESIS
In this thesis we aimed to study the value of serum biomarkers to address the aforementioned major unmet needs in SpA. The main aims were as follows:
1. Diagnosis: to identify (bio-)markers (clinical, imaging and laboratory markers) which can help diagnosing SpA in the early phases of the clinically established disease or already during the subclinical phases of the disease;
2. Treatment response: to identify serum biomarkers for treatment responses in small-scale, short-term, PoC trials, and to validate outcome measures for peripheral SpA;
3. Treatment response: to identify outcome measures for peripheral SpA;4. Outcome: to identify biomarkers which are predictive for the progression of structural
damage in the spine in axial SpA.
13
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Early diagnosis
Concerning the first unmet need, i.e. markers for early SpA diagnosis, there are no serum markers known in literature that are able to diagnose a patient with SpA at the early phase of the disease. In order to address this unmet need, we used three different approaches, with the ultimate goal to find early diagnostic biomarkers. In chapter 2, we performed a literature search in the field of psoriasis and inflammatory bowel disease (IBD), both disorders which are clinically, genetically, and pathophysiologically related to SpA, in order to find potential new serum biomarkers of interest for SpA. In chapter 3, we determined the value of serum biomarkers to discriminate SpA from non-SpA in a cohort of patients with early inflammatory back pain. First, we evaluated the discriminative and diagnostic value of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and calprotectin, all of which are known to be elevated in active axial SpA.33,34 Second, we explored whether the informative serum biomarkers in psoriasis and IBD (as mentioned in chapter 2), namely human beta defensin-2 (hBD-2) and lipocalin-2 (LCN-2), are elevated in the cohort of active axial SpA versus healthy controls. Third, we also checked if IL-27, an IL-12 family cytokine, is elevated in full blown AS when compared to healthy controls as indicated in a recent report.
In chapter 4, we performed a systematic screening in seemingly healthy first-degree relatives (FDRs) of HLA-B27 positive AS patients, since FDRs are at a high risk of developing SpA. In this early phase of SpA, we attempt to identify pre- or subclinical biomarkers, and imaging alterations in these FDRs without SpA symptoms.
Treatment response
Concerning the second unmet need, i.e. markers for treatment response, it is important to have objective markers which give quick go or no-go signals on whether a new treatment is effective at the group level in PoC trials. In chapter 5 we determined which serum biomarkers were able to reflect quickly and reproducibly clinical responses at the group level in PoC trials in SpA. These markers may be useful to predict a clinical response in larger and/or longer term trials. Additionally, in chapter 6 we performed an analysis in two independent randomized controlled trials to determine which clinical disease outcome measures do best reflect disease activity- and treatment responses in peripheral SpA.
Prediction of structural damage
Concerning the fourth unmet need, i.e. halting new bone formation, it is important to predict which patients will develop rapidly progressive new bone formation of the spine. Smoking, HLA-B27 positive status, male gender, and a high disease activity have all been reported to be associated with more rapid progression of structural damage in AS.35–37 Also serum biomarkers such as CRP,38,39 matrix metalloproteinase (MMP-3)40, dickkopf-1 (Dkk-1),36,41,42 visfatin and leptin,43–45 and vascular endothelial growth factor (VEGF)46 have
14 GENERAL INTRODUCTION
been reported to be associated with structural damage of the spine but none of these aforementioned biomarkers could reproducibly predict progression of structural damage in individual patients. In chapter 7, we determined whether serum levels of calprotectin are an independent predictor for new bone formation in axial SpA.
Finally, chapter 8 provides a general discussion and summary of the findings of this thesis.
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REFERENCES
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2. Bakland G, Nossent HC, Gran JT. Incidence and prevalence of ankylosing spondylitis in Northern Norway. Arthritis Rheum 2005;53(6):850–5.
3. Brandt HC, Spiller I, Song I-H, et al. Performance of referral recommendations in patients with chronic back pain and suspected axial spondyloarthritis. Ann Rheum Dis 2007;66(11):1479–84.
4. Poddubnyy D, Vahldiek J, Spiller I, et al. Evaluation of 2 screening strategies for early identification of patients with axial spondyloarthritis in primary care. J Rheumatol 2011;38(11):2452–60.
5. Sieper J, Srinivasan S, Zamani O, et al. Comparison of two referral strategies for diagnosis of axial spondyloarthritis: the Recognising and Diagnosing Ankylosing Spondylitis Reliably (RADAR) study. Ann Rheum Dis 2013;72(10):1621–7.
6. Salvadorini, F. Bandinelli, A. Delle Sedie, L. Riente, A. Candelieri, S. Generini, N. Possemato, S. Bombardieri MM-C. Ankylosing spondylitis: how diagnostic and therapeutic delay have changed over the last six decades. Clin Exp Rheumatol 2012;30(4):561–5.
7. Sorensen J, Hetland ML. Decreases in diagnostic delay are supported by sensitivity analyses. Ann Rheum Dis 2014;73(7):e45–e45.
8. Van Den Bosch F, Kruithof E, Baeten D, et al. Randomized double-blind comparison of chimeric monoclonal antibody to tumor necrosis factor alpha (infliximab) versus placebo in active spondylarthropathy. Arthritis Rheum 2002;46(3):755–65.
9. Braun J, Brandt J, Listing J, et al. Treatment of active ankylosing spondylitis with infliximab: a randomised controlled multicentre trial. Lancet 2002;359(9313):1187–93.
10. Mease PJ, Goffe BS, Metz J, VanderStoep A, Finck B, Burge DJ. Etanercept in the treatment of psoriatic arthritis and psoriasis: a randomised trial. Lancet 2000;356(9227):385–90.
11. Paramarta JE, De Rycke L, Heijda TF, et al. Efficacy and safety of adalimumab for the treatment of peripheral arthritis in spondyloarthritis patients without ankylosing spondylitis or psoriatic arthritis. Ann Rheum Dis 2013;72(11):1793–9.
12. Sieper J, van der Heijde D, Dougados M, et al. Efficacy and safety of adalimumab in patients with non-radiographic axial spondyloarthritis: results of a randomised placebo-controlled trial (ABILITY-1). Ann Rheum Dis 2013;72(6):815–22.
13. Van der Heijde D, Kivitz A, Schiff MH, et al. Efficacy and safety of adalimumab in patients with ankylosing spondylitis: results of a multicenter, randomized, double-blind, placebo-controlled trial. Arthritis Rheum
2006;54(7):2136–46.
14. Landewé R, Braun J, Deodhar a, et al. Efficacy of certolizumab pegol on signs and symptoms of axial spondyloarthritis including ankylosing spondylitis: 24-week results of a double-blind randomised placebo-controlled Phase 3 study. Ann Rheum Dis 2014;73(1):39–47.
15. Van der Heijde D, Landewé R, Einstein S, et al. Radiographic progression of ankylosing spondylitis after up to two years of treatment with etanercept. Arthritis Rheum 2008;58(5):1324–31.
16. Van der Heijde D, Landewé R, Baraliakos X, et al. Radiographic findings following two years of infliximab therapy in patients with ankylosing spondylitis. Arthritis Rheum 2008;58(10):3063–70.
17. Van der Heijde D, Salonen D, Weissman BN, et al. Assessment of radiographic progression in the spines of patients with ankylosing spondylitis treated with adalimumab for up to 2 years. Arthritis Res Ther 2009;11(4):R127.
18. Baraliakos X, Listing J, Brandt J, et al. Clinical response to discontinuation of anti-TNF therapy in patients with ankylosing spondylitis after 3 years of continuous treatment with infliximab. Arthritis Res Ther 2005;7(3):R439–44.
19. Paramarta JE, Heijda TF, Baeten DL. Fast relapse upon discontinuation of tumour necrosis factor blocking therapy in patients with peripheral spondyloarthritis. Ann Rheum Dis 2013;72(9):1581–2.
20. Garrett S, Jenkinson T, Kennedy LG, Whitelock H, Gaisford P, Calin A. A new approach to defining disease status in ankylosing spondylitis: the Bath Ankylosing Spondylitis Disease Activity Index. Rheumatology 1994;21(12):2286–91.
21. Lukas C, Landewé R, Sieper J, et al. Development of an ASAS-endorsed disease activity score (ASDAS) in patients with ankylosing spondylitis. Ann Rheum Dis 2009;68(1):18–24.
22. Gruttola VG De, Clax P, Demets DL, et al. Considerations in the Evaluation of Surrogate Endpoints in Clinical Trials: Summary of a National Institutes of Health Workshop. Control Clin Trials 2001;1998(2001):485–502.
23. Bos WH, Wolbink GJ, Boers M, et al. Arthritis development in patients with arthralgia is strongly associated with anti-citrullinated protein antibody status: a prospective cohort study. Ann Rheum Dis 2010;69(3):490–4.
24. Nielen MMJ, van Schaardenburg D, Reesink HW, et al. Specific autoantibodies precede the symptoms of rheumatoid arthritis: a study of serial measurements in blood donors. Arthritis Rheum 2004;50(2):380–6.
25. Nishimura K, Sugiyama D, Kogata Y, Tsuji G, Nakazawa T. Annals of Internal Medicine Review Meta-analysis : Diagnostic Accuracy of Anti–Cyclic Citrullinated Peptide
16 GENERAL INTRODUCTION
Antibody and Rheumatoid Factor for Rheumatoid Arthritis. Ann Intern Med 2015;797.
26. Joensuu H, Kellokumpu-Lehtinen P-L, Bono P, et al. Adjuvant docetaxel or vinorelbine with or without trastuzumab for breast cancer. N Engl J Med 2006;354(8):809–20.
27. Konecny GE, Thomssen C, Lück HJ, et al. Her-2/neu gene amplification and response to paclitaxel in patients with metastatic breast cancer. J Natl Cancer Inst 2004;96(15):1141–51.
28. Romond EH, Perez EA, Bryant J, et al. Trastuzumab plus Adjuvant Chemotherapy for Operable HER2-Positive Breast Cancer. N Engl J Med 2005;353:1673–84.
29. Pritchard KI, Shepherd LE, O’Malley FP, et al. HER2 and responsiveness of breast cancer to adjuvant chemotherapy. N Engl J Med 2006;354(20):2103–11.
30. Giorgi J V, Lyles RH, Matud JL, et al. Predictive value of immunologic and virologic markers after long or short duration of HIV-1 infection. J Acquir Immune Defic Syndr 2002;29:346–55.
31. Mellors JW, Munoz A, Giorgi J V, et al. Plasma Viral Load and CD4 + Lymphocytes as Prognostic Markers of HIV-1 Infection. Ann Intern Med 1997;126:946–54.
32. Bruisten S, Frissen PHJ, Swieten PVAN, et al. Prospective Longitudinal Analysis of Viral Load and Surrogate Markers in Relation to Clinical Progression in HIV Type 1-Infected Persons. AIDS Res Hum Retroviruses 1997;13(4):327–35.
33. Kane D, Roth J, Frosch M, Vogl T, Bresnihan B, FitzGerald O. Increased perivascular synovial membrane expression of myeloid-related proteins in psoriatic arthritis. Arthritis Rheum 2003;48(6):1676–85.
34. De Rycke L, Baeten D, Foell D, et al. Differential expression and response to anti-TNFalpha treatment of infiltrating versus resident tissue macrophage subsets in autoimmune arthritis. J Pathol 2005;206(1):17–27.
35. Ramiro S, Stolwijk C, van Tubergen A, et al. Evolution of radiographic damage in ankylosing spondylitis: a 12 year prospective follow-up of the OASIS study. Ann Rheum Dis 2015;74(1):52–9.
36. Heiland GR, Appel H, Poddubnyy D, et al. High level of functional dickkopf-1 predicts protection from syndesmophyte formation in patients with ankylosing spondylitis. Ann Rheum Dis 2012;71(4):572–4.
37. Ramiro S, van der Heijde D, van Tubergen A, et al. Higher disease activity leads to more structural damage in the spine in ankylosing spondylitis: 12-year longitudinal data from the OASIS cohort. Ann Rheum Dis 2014;73(8):1455–61.
38. Poddubnyy D, Rudwaleit M, Haibel H, et al. Rates and predictors of radiographic sacroiliitis progression over 2 years in patients with axial spondyloarthritis. Ann Rheum Dis 2011;70(8):1369–74.
39. Pedersen SJ, Sørensen IJ, Lambert RGW, et al. Radiographic progression is associated with resolution of systemic inflammation in patients with axial spondylarthritis treated with tumor necrosis factor α inhibitors. Arthritis Rheum 2011;63(12):3789–800.
40. Yang C, Gu J, Rihl M, et al. Serum levels of matrix metalloproteinase 3 and macrophage colony-stimulating factor 1 correlate with disease activity in ankylosing spondylitis. Arthritis Rheum 2004;51(5):691–9.
41. Klingberg E, Nurkkala M, Carlsten H, Forsblad-d’Elia H. Biomarkers of bone metabolism in ankylosing spondylitis in relation to osteoproliferation and osteoporosis. J Rheumatol 2014;41(7):1349–56.
42. Korkosz M, Jerzy G, Leszczy P, Pawlak-bu K, Jeka S, Kucharska E. High disease activity in ankylosing spondylitis is associated with increased serum sclerostin level and decreased wingless protein-3a signaling but is not linked with greater structural damage. BMC Musculoskelet Disord. 2013; 14:99.
43. Kim K-J, Kim J-Y, Park S-J, et al. Serum leptin levels are associated with the presence of syndesmophytes in male patients with ankylosing spondylitis. Clin Rheumatol 2012;31(8):1231–8.
44. Syrbe U, Callhoff J, Conrad K, et al. Serum adipokine levels in patients with ankylosing spondylitis and their relationship to clinical parameters and radiographic spinal progression. Arthritis Rheumatol (Hoboken, NJ) 2015;67(3):678–85.
45. Genre F, López-Mejías R, Miranda-Filloy J a, et al. Adipokines, biomarkers of endothelial activation, and metabolic syndrome in patients with ankylosing spondylitis. Biomed Res Int 2014;2014:860651.
46. Poddubnyy D, Conrad K, Haibel H, et al. Elevated serum level of the vascular endothelial growth factor predicts radiographic spinal progression in patients with axial spondyloarthritis. Ann Rheum Dis 2014;73(12):2137–43.
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Serum biomarkers in spondyloarthritis-
related diseases: lessons from psoriasis and
inflammatory bowel diseases
Maureen C. Turina, Robert Landewé, Dominique L. Baeten
Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology and
immunology Center, Academic Medical Center/University of Amsterdam, Amsterdam,
The Netherlands
Submitted for publication
2
20 SERUM BIOMARKERS IN PSORIASIS AND IBD
SUMMARY
Early diagnosis, monitoring of disease activity, prediction of treatment response, and structural outcome remain major challenges in spondyloarthritis (SpA). Biomarkers could play a role in addressing these challenges, but in SpA there is a lack of suitable biomarkers. As SpA is clinically and pathophysiologically closely related to psoriasis and inflammatory bowel disease (IBD), we reviewed the value of serum biomarkers in these conditions with the aim to find potential candidates for assessing SpA. Candidates of interest were antimicrobial peptides, including human beta defensin-2 (hBD-2) and lipocalin-2 (LCN-2), and class-1 MHC molecule beta2-microglobulin. Since these biomarkers are relevant in psoriasis and/or IBD from a pathophysiological point of view, and may play a role in the pathogenesis of SpA, we recommend further exploration of their value as biomarker in the diagnosis and prognosis of SpA.
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CHAPTER 2
UNMET NEEDS IN SPONDYLOARTHRITIS
Spondyloarthritis (SpA) is an immune-mediated inflammatory disease affecting the spine, the peripheral joints and extra-articular tissues such as the skin, the gut, and the eye.1 The pathology of SpA is characterized by a combination of chronic tissue inflammation, destruction of cartilage and bone, and pathological new bone formation, that may lead to ankylosis. Despite major advances in the field, such as the use of magnetic resonance imaging (MRI) to detect spinal inflammation and to find appropriate patients for treatment with TNF blockers,2–8 several important challenges remain to be addressed.
First, there is a huge diagnostic delay of approximately 5-10 years between the onset of SpA symptoms and the diagnosis.9–11 This delay is due to the fact that the early clinical signs and symptoms are often non-specific, that pathognomonic features of SpA, such as radiologic sacroiliitis, only appear late in the disease course, and that well-known biological markers such as HLA-B27 lack specificity (many healthy individuals carry HLA-B27) and therefore predictive value in the diagnostic context. Second, good biological predictors for treatment response are lacking. Currently, the only informative marker is C-reactive protein (CRP). Nevertheless, CRP as a marker for treatment response falls short because only one third of the patients have elevated CRP levels prior to treatment. Third, the progression rate of new bone formation as observed on consecutive X-rays of the lumbar and cervical spine is very slow and besides only occurs in a relatively small group of patients. Currently, markers predicting which patients will develop significant new bone formation are lacking.
Overall, an early diagnosis, a proper prediction of structural damage, as well as prediction of treatment response, all in individual patients, remain major challenges in SpA. Biomarkers could be of value in addressing these challenges.
BIOMARKERS IN SPONDYLOARTHRITIS
A biomarker is a “characteristic that can be objectively measured and evaluated as an indicator of a normal biologic process, a pathophysiologic process, or a pharmacologic response to a therapeutic intervention”.12 A biomarker should be sensitive, specific, reproducible, and deriving the biomarker from a patient should preferably be a non-invasive procedure. Taking these criteria into account, biomarkers can have an important role to fulfill the previously defined unmet needs in the process of diagnosis, treatment response and prognosis. Several biomarkers have already been studied in SpA. Common markers of systemic inflammation such as CRP and erythrocyte sedimentation rate (ESR) have been used for a long time in the clinical care of SpA patients. Accordingly, elevated CRP is included as a criterion in the ASAS classification criteria for axial SpA criteria but not for ASAS peripheral SpA criteria.2,13
22 SERUM BIOMARKERS IN PSORIASIS AND IBD
When elevated, CRP levels may correlate with disease activity measures and decrease upon effective treatment.14–17 Moreover, CRP appears to be a predictor for radiographic axial progression.18 However, CRP and ESR are only elevated in 30 to 50% of the SpA patients with clinical signs and symptoms of active disease and inflammation14–17 and, obviously, are not specific for SpA. The limited sensitivity and specificity explains why CRP and ESR can be useful biomarkers at the group level (such as in clinical trials) but lack sufficient predictive value to be used in individual patients.
Other serum markers of inflammation that have been studied in SpA are Interleukin-6 (IL-6) and calprotectin. IL-6 is the main driver of CRP and, similar to CRP, serum IL-6 levels are significantly increased in active SpA and decrease upon clinical response after tumour necrosis factor (TNF) blockade.19,20 The calcium-binding protein calprotectin, a heterodimer of S100A8 and S100A9, is expressed and secreted during monocyte infiltration into inflamed tissues, including macrophage infiltration in synovial tissue of SpA patients.21,22 Calprotectin serum levels are elevated in SpA, correlate moderately well (r=0.40-0.60) with disease activity, and decrease upon TNF blockade.21–23 Moreover, calprotectin serum levels is an independent predictor for radiological axial progression at the group level.24 Two other biomarkers that were studied in SpA are more related to the pathological processes than to inflammation as such. Vascular endothelial growth factor (VEGF), a growth factor involved in neo-angiogenesis, may be involved in the pronounced hypervascularity in SpA synovitis.25,26 Serum VEGF levels are significantly elevated in SpA versus healthy controls and significantly albeit moderately at best correlate (r=0.22-0.44) with disease activity, but levels do not decrease after short-term treatment with TNF blockers.20,27 Whereas an original report indicated that serum VEGF levels were predictive of new bone formation,28 these results could not be confirmed by others.29
Matrix metalloproteinase-3 (MMP-3) is an enzyme involved in tissue remodelling and cartilage damage. MMP-3 expression was elevated in synovial tissue, synovial fluid and serum in SpA and this expression correlated well with disease activity30–34 and normalized upon effective treatment.30
With regard to predicting new bone formation in ankylosing spondylitis (AS), the prototype of axial SpA, most studies have focused on molecules involved in the regulation of osteoblast activity, including the wnt-pathway, which is involved in the process of new bone formation. Dickkopf-1 (DKK1) and sclerostin are inhibitors of this pathway, and Diarra et al.35 found that serum DKK1 levels were decreased in AS patients versus healthy controls or rheumatoid arthritis patients and low levels were associated to radiographic axial progression as expressed by syndesmophytes formation. These results were confirmed by others.36–38 For sclerostin, discordant results were seen regarding the relationship with radiographic axial spinal progression.36,39–42
Finally, several studies have screened for disease-specific autoantibodies as potential
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diagnostic biomarker in SpA. Unfortunately, most studies did not find disease-specific autoantibodies and the few that were reported could not be independently confirmed.43–45 Recently, one group found elevated levels of IgG autoantibodies CD74 specific for HLA class II-associated invariant chain peptide (CLIP) in SpA.46,47 These data as well as the diagnostic value of this autoantibody should be validated in independent cohorts.
In summary, despite major efforts over the last years only few biomarkers have been described and validated in SpA, and often these biomarkers are useful at the group level but lack specificity to be used in individual patients in clinical care. Interestingly, SpA is genetically, pathophysiologically and clinically associated with psoriasis and inflammatory bowel diseases (IBD), two conditions in which serum biomarkers have been described. Therefore, we reviewed here the value of biomarkers in these conditions and discuss their potential utility for SpA. Reviewing was done for the settings of diagnosis (i.e. difference between disease and healthy or disease and similar inflammatory diseases), with respect to correlation with disease activity and response to effective treatment, as well as for predicting structural damage (in axial SpA). We have evaluated both the pathophysiological and clinical value of these markers.
SERUM BIOMARKERS IN PSORIASIS
Psoriasis is an immune-mediated, chronic inflammatory disease primarily of the skin but can also affect nails and peripheral and axial joints. The disease is characterized by abnormal differentiation and hyperproliferation of epidermal keratinocytes and infiltration of immune cells. Roughly 1 in 5 psoriasis patients will develop psoriatic arthritis (PsA), one of the phenotypical forms of SpA.48 At the genetic level, SNPs in IL-23R and Th-17 genes have shown to be associated with both psoriasis and SpA.
In clinical practice, a diagnosis of psoriasis is based on clinical history and examination and, in case of diagnostic uncertainty, skin biopsies. Disease activity is mainly determined by the Psoriasis Area and Severity Index (PASI),49 which includes the percentage of affected skin area, the erythema, the induration, and scaling. Currently, serum biomarkers do not play an important role in clinical practice but are extensively studied in clinical trials (Table 1).
Serum CRP levels were found to be elevated in the moderate and severe forms of psoriasis but not in patients with mild disease, when compared with the healthy individuals.50,51 Several studies have reported CRP elevation in 17-45.7% of the psoriasis patients versus 1% in the control group.51–53 Furthermore, CRP levels decreased significantly after effective treatment was started.51,54–57 It is therefore only a potentially useful marker for disease activity in patients who did not receive systemic treatment for at least one month. In the treated patients, PASI is preferred to monitor disease activity. ESR levels were elevated in
24 SERUM BIOMARKERS IN PSORIASIS AND IBD
Table 1. Serum biomarkers in psoriasis: elevation in comparison with healthy controls, correlation with disease activity according to PASI, and modulation by effective treatment
Biomarker
Elevation incomparison with healthy controls
Correlation withdisease activitymeasured PASI Treatment response References
approximately half of the psoriasis patients compared to healthy controls. Elevated ESR was clearly more frequent in the active state of the disease (80%) versus non-active psoriasis.58
Cytokines, including interferon-gamma (IFNγ), TNF-α, TNF-R1, IL-6, IL-8, IL-12, and IL-18, IL-22, and IL-23 have been investigated thoroughly in psoriasis. Coimbra et al. and others59–63 have found that the serum levels of these cytokines were overall significantly higher in psoriasis as compared with healthy controls. But the data on the correlation with PASI were rather conflicting. Psoriasis-specific treatment including methotrexate, UV-A/UV-B treatment, and TNF blockade did have an effect on serum levels of these cytokines.59,60,64,65
Adhesion molecules are expressed by activated tissue cells (e.g. endothelium) as well as leukocytes and allow selective migration of distinct leukocyte subsets to specific tissues and
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sites of inflammation. For example, activated epithelial cells express E-selectin, which can interact with E-selectin on another epithelial cell or with alpha E beta 7 (a member of the integrin family) on CD8 positive T cells. Of the soluble adhesion molecules that can easily be measured in serum, E-selectin, ICAM-1, and VAP-1 are best studied in psoriasis.63,66–74 All of these molecules showed elevated serum levels in psoriasis versus healthy controls. Soluble E-selectin and ICAM-1 levels, however, were consistently (but only weakly to moderately) associated with disease activity as expressed by PASI scores (r=0.44 and r=0.26-0.43, respectively). Accordingly, only E-selectin levels decreased significantly and consistently upon effective treatment.63,67,68,71,72
Among the antimicrobial peptides and proteins (AMP), calprotectin (S100A8/A9 proteins), lipocalin-2 (LCN-2, also called neutrophil gelatinase-associated lipocalin [NGAL]), and human β-defensin-2 (hBD-2) were associated with psoriasis. Highly up-regulated calprotectin levels were found in a proteomic analysis of the epidermis from psoriasis patients.75 In addition, Benoit et al.76 showed that calprotectin levels in serum were significantly elevated when compared to healthy controls and that patients with a high PASI (>15) score also had higher levels of calprotectin. Regarding LCN-2 serum levels, several groups consistently found elevated levels in psoriasis patients when compared with healthy individuals. However, absent or only weak (r=0.27) correlations were found between LCN-2 levels and PASI scores, and serum levels were not normalized by effective treatment.77–80 Serum levels of another AMP, hBD-2, were elevated consistently when compared with healthy donors. Jansen et al.81 reported a high correlation with PASI (r=0.82), whereas another group did not see such a strong correlation (r<0.1, p>0.05).82
Adipokines are produced by fat (adipose) tissue and play a role in metabolic processes, but these proteins are also associated with inflammation. Extensively studied adipokines were resistin, leptin, adiponectin, ghrelin, and retinol binding protein-4 (RBP-4). With the exception of adiponectin, all serum and plasma adipokine levels were significantly higher in psoriasis versus healthy individuals.80,83–89 Only resistin levels correlated weakly with PASI (r2=0.027) and none of the adipokines consistently showed a normalization in levels after effective treatment.80,85,88,90–92
Growth factors are involved in angiogenesis and hypervascularity in psoriasis and are well studied as biomarkers. Of these growth factors, VEGF was the most evaluated markers. VEGF was the most promising in psoriasis, since there were differences in serum levels between psoriasis patients and healthy controls and there was a strong correlation (R=0.65) with PASI.59,93,94 However, serum levels did not normalize upon effective treatment.59,62,95
Nitric oxide (NO) is a free radical and is secreted by various cell types, including fibroblasts and endothelial cells. Tekin et al.96 performed a study in 22 psoriasis samples versus 21 healthy controls and found significantly higher serum levels in the former group. These results were reproduced by others.94,97,98 Furthermore, NO plasma and serum levels
26 SERUM BIOMARKERS IN PSORIASIS AND IBD
decreased after effective treatment.96
In summary, CRP, ESR, IL-18, IL-22, ICAM-1, calprotectin, LCN-2, hBD-2, VEGF, RBP-4, and NO were the most informative biomarkers since these markers are elevated in patients with the disease when compared to healthy controls, show weak to moderate correlations with disease activity, and/or decrease upon effective treatment at the group level, indicating that -at least from a pathophysiological point of view- these are interesting markers. In spite of this, though, the value of these markers as biomarker in clinical practice (at the individual patient level) seems –if investigated- modest at best. In psoriasis, CRP and ESR were the only serum biomarkers used in clinical practice for the evaluation of treatment, despite the disappointing results earlier mentioned. The most interesting serum and plasma biomarkers in psoriasis from a pathophysiological point of view are the antimicrobial peptides hBD-2 and LCN-2: the expression of both peptides is driven by IL-17 and may therefore reflect a key pathophysiological process in psoriasis skin, although the role in clinical practice remains inconclusive.
SERUM BIOMARKERS IN IBD
IBD includes Crohn’s disease (CD) and ulcerative colitis (UC). Peripheral arthritis and sacroiliitis are seen in 7-16%100–102 and 2-32%100,102,103 of the IBD patients, respectively. Similarly, 60-70% of the SpA patients show subclinical signs of gut inflammation on biopsies obtained by ileocolonscopy,104,105 but only 7% of these patients will eventually develop clinically overt IBD over time. The link between SpA and IBD is corroborated by genetic studies, with the best example being polymorphisms in the interleukin 23 receptor (IL23R) gene which are associated both with IBD (OR 0.38 and 0.73 for CD and UC, respectively) and AS (OR=0.53-1.27).106–109
The diagnosis of IBD in clinical practice is based on the combination of clinical history, physical examination, stool findings (i.e. calprotectin and lactoferrin), serological antibodies, inflammatory markers in blood, and colonoscopy.110 The major clinical outcome measure in Crohn’s disease, the Crohn’s Disease Activity Index (CDAI),111 includes clinical and laboratory findings to determine disease activity. In UC, several scores are used to determine disease activity including clinical and endoscopic scores. A frequently used clinical score is Simple Clinical Colitis Activity Index (SCCAI).112 The Mayo activity index is based on clinical as well as endoscopic findings.113
Of the acute phase reactants, CRP was found to be a biomarker for IBD since the serum levels were elevated in CD and to a lesser extent in UC when compared with healthy controls or functional bowel disorders.114,115 Elevated levels were correlated with a higher disease activity.116–118 Louis et al.118 studied a group of 226 CD patients receiving TNF-inhibitors and
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a clinical response was associated with a decrease in CRP with similar results in a larger cohort. There were discrepant data about the ability of CRP to predict disease relapse.119,120 Other well studied inflammatory markers were ESR, procalcitonin, and YKL-40. All three markers correlated with the disease activity but only ESR and procalcitonin differentiated between IBD and healthy individuals or other gastrointestinal diseases.121–128 Moreover, a trend towards elevated levels of YKL-40 was found in more severe CD patients having strictures (i.e. narrowing of the intestinal lumina),124 but since the majority of active patients do not have elevated levels, in clinical practice YKL-40 is of little value.
Cytokines measured in serum did not seem to be important markers of disease in IBD, despite their role in the inflammatory process.129,130 The only potential marker is IL-6, the main driver of CRP. Levels of IL-6 in serum were increased in active CD compared with healthy controls but correlation with disease activity was weak.131–133
Of the soluble adhesion molecules, ICAM-1 was the most promising serum and plasma marker as the levels were elevated when compared with healthy controls. Although discrepant data are available on correlation with disease activity, effective treatment down-regulates ICAM-1 levels.134–138 E-selectin levels in serum or plasma were significantly higher in IBD than in healthy controls. However, there was no significant association between disease activity and treatment.134–138 A few studies were published on vascular cell adhesion molecule (VCAM). The serum or plasma levels in IBD were not consistently elevated versus healthy controls and correlations to disease activity were poor.134–136
The adipokines adiponectin, leptin, ghrelin, resistin, and vaspin had been investigated thoroughly in IBD. Only serum levels of resistin and vaspin were consistently elevated in IBD versus healthy individuals. Moreover, strong correlations with PASI were found for ghrelin, resistin and vaspin levels with disease activity.139–147 Ghrelin and resistin levels were decreased upon effective treatment but this was not studied for the other adipokines.148,149
Of the S100 proteins, S100A12 levels in serum were elevated in IBD when compared with healthy controls, but there are conflicting data about the correlation with active disease activity.150,151 Serum levels of S100A8/S100A9, calprotectin, were elevated in IBD versus healthy individuals and correlated with the CDAI.152–154 Similar results were seen in children using pediatric CDAI indices.155 Furthermore, calprotectin serum levels decreased upon treatment with TNF inhibition.154,156 Fecal calprotectin is one of the most extensively studied stool markers in IBD. Calprotectin levels in stool can differentiate between IBD and healthy controls or irritable bowel syndrome (IBS). One meta-analysis of Von Roon et al.157 included 30 studies with 1210 IBD patients, 297 colorectal cancer, 697 IBS, and 3393 healthy controls and reported that fecal calprotectin is a useful biomarker to differentiate between IBD and non-IBD patients. The overall weighted area under curve (AUC) was with 0.95-0.98 (using a cut-off level of 50 ug/g and 100ug/g, respectively) exceptionally high. Moreover, differentiating CD from IBS by fecal calprotectin showed an AUC of 0.97. Van Rheenen et
28 SERUM BIOMARKERS IN PSORIASIS AND IBD
al.158 determined that fecal calprotectin could be used as screening tool in suspected clinical IBD, thereby decreasing the use of invasive colonoscopy by 67%, but at the cost of false negative results in 6% of the cases. Results of a meta-analysis that included 13 studies (1471 IBD patients), showed that fecal calprotectin is also a good marker for disease activity based on the Mayo activity index.159 Moreover, fecal calprotectin decreased upon treatment160–163 and may predict disease relapse.120,164,165
Several AMPs have been investigated in IBD. Serum LCN-2 (NGAL) levels were elevated in IBD when compared with healthy controls and IBS.166–168 HBD-2 seemed a potential marker since expression levels were increased in inflamed mucosa versus non-inflamed mucosa of the colon.169 However, Yamaguchi et al. found no differences in hBD-2 plasma levels in UC or CD when compared to healthy controls.170
Beta-2-microglobulin (β2-M), which forms a part of the major histocompatibility complex class 1 (MHC 1), had been investigated in two independent studies. In 2001 Zissis et al.171 showed that serum levels were elevated in CD versus healthy controls, and that serum levels were higher when patients had a higher disease activity, but they did not see similar results for UC. Yilmaz et al.172 recently showed similar results but now in the whole IBD population.
Of the serological antibodies studied in IBD,173–177 anti-saccharomyces cervisiae antibodies (ASCA) and perinuclear anti-neutrophil cytoplasmic antibodies (pANCA) showed the highest diagnostic accuracy. Sensitivity and specificity for ASCA were 60% and 91% and for pANCA 50% and 95% respectively, when distinguishing IBD from healthy controls. Sensitivity and specificity for distinguishing between CD and UC were for ASCA (CD): 60% and 86%, and for pANCA (UC): 50% and 94% respectively.178 Similar results were seen in other studies.179,180 Also, when discriminating CD from UC or when comparing with other gastrointestinal diseases, including celiac disease, the specificity was too low for these antibodies.174–178 Both autoantibodies had a positive predictive value of 80-90% and a negative predictive value of 50-80%. The number of false-positive and false-negative individual was too high to recommend these autoantibodies for routine diagnostic procedures. Ester et al.181 found no association of ASCA or pANCA with response to infliximab treatment, but ASCA positivity was associated with worse disease progression: a more severe disease type (from inflammation to structuring (or stenosis) and penetrating) disease in CD.182 Recently, Bonneau et al.183 published a systematic review in which anti-glycan, anti-GP2, and anti-GM-CSF antibodies were also described as having low sensitivity but high specificity to CD when compared with UC but the contribution of these antibodies to diagnosis is not yet clear.
To summarize, CRP and ESR, the S100 family proteins S100A12 and S100A8/A9 (calprotectin), the antimicrobial peptides LCN-2 and hBD-2, the MHC class 1 molecule β2-M, and ASCA antibodies are of interest as biomarkers in IBD from a pathophysiological point of view. In clinical practice however, only a few of these markers are used, including CRP, ESR, and fecal calprotectin. Since CRP correlates with disease activity and CRP levels normalize upon
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effective treatment, evaluation of therapy by CRP is often applied in general practice. Fecal calprotectin, but not serum calprotectin, is extensively used in clinical practice to identify IBD patients with intestinal inflammation, providing high sensitivity and specificity in detecting IBD. Nevertheless, the ileocolonoscopy remains the gold standard. With regard to antibodies, ASCA antibodies are able to differentiate between CD and UC and are used in clinical practice although not as a screening diagnostic procedure. Other markers in IBD that are of pathophysiological interest are the IL-17 driven LCN-2, hBD-2, and β2-M, that forms part of the MHC class-I molecule (Table 2).
Table 2. Serum biomarkers in IBD levels: elevation in comparison with healthy controls, correlation with disease activity according to CDAI, SCCAI, or endoscopic activity, modulation by effective treatment, and outcome of structural damage
Biomarker
Elevation In comparison with healthy controls
Correlation with disease activity measured by CDAI or SCCAI or endoscopic activity
Treatment response
Outcome structural damage References
CRP + + + + [114–121]ESR + + NA NA [114, 128]Procalcitonin + +/- NA NA [125–127]YKL-40 +/- + NA +/- [122–124]IL-6 + +/- NA NA [131–133, 156]ICAM-1 +/- - + NA [134–138]E-selectin + - - NA [134–138]VCAM +/- - - NA [134–136]Adiponectin + - - NA [145–147, 149, 184]Leptin +/- - +/- NA [145, 146, 148, 149, 184]Ghrelin + + + +/- [140, 141, 146, 184, 185]Resistin + +/- + NA [142, 143, 146, 149, 184]Vaspin +/- - NA NA [144]S100A12 + +/- + NA [150, 151]S100A8/A9 + NA NA + [152–155]LCN-2 + + NA NA [166–168]hBD-2 - - NA NA [169, 170]β2-M + + NA NA [171, 172]
Several biomarkers studied in psoriasis and IBD may be informative in SpA as well. CRP, ESR, calprotectin, and VEGF are interesting in psoriasis and IBD. These markers have already been studied in SpA (as mentioned above). While they may be discriminatory at the group level, sensitivity and/or specificity are too low to be used in clinical practice for diagnosis, disease activity measurement, evaluation of treatment response, or prediction of axial spinal progression.
Some of the biomarkers of interest in in psoriasis and IBD have also been studied in SpA. Negative or variable results were found for serum-IL-18,186 ICAM-1,187–189 RBP-4,190,191 and NO.192,193
ASCA antibodies can help to discriminate CD from UC, have already been studied in SpA. The levels of ASCA antibodies were found to be higher in SpA patients than in healthy controls, as reported by different studies.194,195 One study determined these antibodies in non-IBD SpA patients, and 30% of them appeared to be ASCA-positive. Nevertheless, levels did not correlate with disease activity.196
The AMPs are a new family of relevant biomarkers in psoriasis and IBD as was found in several studies. AMPs have not yet been extensively studied in SpA. The most interesting members of this family are LCN-2 and hBD-2, both of which are driven by IL-17 and are reflecting active disease in psoriasis as well as IBD. And because the reliable measurement of IL-17 in serum remains a challenge, these biomarkers may be used as a proxy for IL-17-mediated tissue inflammation in psoriasis and IBD. As SpA is also an IL-17-driven disease,197–201 these markers certainly deserve further study in this condition. It should be noted, however, that these AMPs are mainly produced by epithelial cells and may thus be more useful in skin and gut diseases than in other IL-17-related inflammatory conditions. Along the same line, IL-22 is an IL-10 cytokine family member which is produced by Th17 cells under the control of IL-23. It was shown that plasma IL-22 levels were increased in SpA versus healthy individuals, but no correlation was found with Bath ankylosing spondylitis disease activity index (BASDAI).202 The reliability of serum IL-22 measurement and the validity of these findings require replication in independent studies.
Another biomarker which was identified in IBD and may be directly related to the pathological processes in SpA is β2-M. β2-M is a component of class I MHC molecules, including HLA-B27, which is (still) the major genetic risk factor for SpA. Although the exact role of HLA-B27 in the disease pathogenesis is not yet clear, several hypotheses suggest that the level of expression of β2-M may modulate the pathological role of HLA-B27. One hypothesis proposes that β2-
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M-free HLA-B27 heavy chains form disulphide-linked homodimers which can be recognized by the KIR3DL2 receptors on NK-cells and T-cells.203 The second hypothesis concerns HLA-B27 heavy chain misfolding prior to binding of β2-M and peptide, resulting in unfolded protein responses (UPR), which subsequently may lead to an inflammatory cytokine release.201,204 Interestingly, modulation of β2-M expression levels in the HLA-B27 transgenic rat model of SpA did profoundly affect the phenotype of the disease,205–207 confirming the potential importance of this molecule in SpA. Therefore, serum β2-M expression levels should be further explored as potential biomarker in SpA.
EXPERT COMMENTARY
To conclude, of the serum biomarkers identified in psoriasis and IBD, the IL-17 driven anti-microbial peptides hBD-2 and LCN-2, and the class I MHC molecule β2-microglobulin are the most interesting candidates from a pathophysiological standpoint to be further explored in SpA for clinical purposes.
KEY POINTS
• SpA is an immune-mediated inflammatory disease affecting the spine, the peripheral joints, and extra-articular tissues such as the skin, the gut, and the eye.
• Serum biomarkers could address several challenges in SpA (diagnosis, disease activity monitoring, treatment response, and outcome).
• Serum biomarkers well studied in spondyloarthritis are CRP, ESR, IL-6, calprotectin, VEGF, MMP-3, DKK-1, and sclerostin.
• Although the aforementioned biomarkers are useful at the group level in SpA, these markers lack specificity for the use in individual patients in clinical care.
• SpA is a clinically and pathophysiologically closely related to psoriasis and inflammatory bowel disease.
• In psoriasis, CRP, ESR, IL-18, IL-22, ICAM-1, calprotectin, LCN-2, hBD-2, VEGF, RBP-4, and NO were the most interesting markers from a pathophysiological standpoint.
• In IBD, CRP and ESR, hBD-2, LCN-2, and ASCA antibodies were of interest from a pathophysiological point of view.
• HBD-2, LCN-2, and β2-microglobulin are the most interesting candidates from a pathophysiological standpoint to be further explored in SpA for clinical purposes.
32 SERUM BIOMARKERS IN PSORIASIS AND IBD
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38 SERUM BIOMARKERS IN PSORIASIS AND IBD
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164. Ferreiro-iglesias R, Acosta MB, Santiago MO, Gonzalez L, Alonso C, Pen D, Estevez JB, Dominguez-mun JE: Fecal Calprotectin as Predictor of Relapse in Patients With Inflammatory Bowel Disease Under Maintenance. J Clin Gastroenterol 2015;00:000–000.
165. Wright EK, Kamm M a, De Cruz P, Hamilton AL, Ritchie KJ, Krejany EO, Leach S, Gorelik A, Liew D, Prideaux L, Lawrance IC, Andrews JM, Bampton P a, Jakobovits SL, Florin TH, Gibson PR, Debinski H, Macrae F a, Samuel D, Kronborg I, Radford-Smith G, Selby W, Johnston MJ, Woods R, Elliott PR, Bell SJ, Brown SJ, Connell WR, Day AS, Desmond P V, et al.: Measurement of fecal calprotectin improves monitoring and detection of recurrence of Crohn’s disease after surgery. Gastroenterology 2015, 148:938–947.e1.
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166. Janas RM, Ochocińska A, Snitko R, Dudka D, Kierkuś J, Teisseyre M, Najberg E: Neutrophil gelatinase-associated lipocalin in blood in children with inflammatory bowel disease. J Gastroenterol Hepatol 2014, 29:1883–9.
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186. Sari I, Kebapcilar L, Taylan A, Bilgir O, Kozaci DL, Yildiz Y, Yuksel A, Gunay N, Akkoc N: Fetuin-A and interleukin-18 levels in ankylosing spondylitis. Int J Rheum Dis 2010, 13:75–81.
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195. Aydin S, Atugunduz P, Temel M, Bicakcigil M, Tasan D, Direskeneli H: Anti-saccharomyces cerevisiae antibodies (ASCA) in spondyloarthropathies: a reassessment. Rheumatology (Oxford) 2008, 47:142–144.
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199. Sarin R, Wu X, Abraham C: Inflammatory disease protective R381Q IL23 receptor polymorphism results in decreased primary CD4 + and CD8 + human T-cell functional responses. Proc Natl Acad Sci 2011, 108:9560–9565.
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Serum inflammatory biomarkers fail to
identify early axial spondyloartritis: results
from the SpondyloArthritis Caught Early
(SPACE)-cohort
Maureen C. Turina1, Nataliya Yeremenko1,2, Floris van Gaalen3, Maikel van Oosterhout4, Inger J. Berg5,
Ramona Ramonda6, Maria C. Lebre2, Robert Landewé1, Dominique L. Baeten1,2
1Amsterdam Rheumatology and Immunology Center, Department of Clinical
Immunology and Rheumatology, Amsterdam Rheumatology and immunology Center,
Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands; 2Department of Experimental Immunology, Academic Medical Center/University of
Amsterdam, Amsterdam, The Netherlands; 3Department of Rheumatology, Leiden University Medical Center, Leiden, The
Netherlands; 4 Department of Rheumatology, Groene Hart Ziekenhuis, Gouda , The Netherlands;
5 Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway; 6 Rheumatology Unit, Department of Medicine- DIMED- University of Padova, Padova
Italy
Submitted for publication
3
44 SERUM INFLAMMATORY MARKERS NOT IN EARLY SpA
ABSTRACT
Introduction
Decreasing the diagnostic delay in axial spondyloarthritis (axSpA) remains a major challenge. Here, we assessed the value of serum inflammatory biomarkers to distinguish early axSpA from other pathologies in a large cohort of patients referred with early back pain.
Methods
Serum c-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and calprotectin were determined in the SPondyloArthritis Caught Early (SPACE) cohort (n=310), an early back pain inception cohort. Additionally, explorative serum biomarkers derived from literature (interleukin-27 [IL-27], human beta-defensin-2 [hBD-2], and lipocalin-2 [LCN-2]) were determined by ELISA in full-blown ankylosing spondylitis (AS) patients (n=21) and healthy controls (n=19).
Results
Serum CRP and ESR levels were not elevated in early axSpA versus ‘control’ back pain patients. Serum calprotectin was elevated in early axSpA versus controls (p=0.01) but failed to identify early axSpA at the individual level (positive predictive value of 38.7%). As to explorative biomarkers, serum levels of IL-27 were not detectable, and hBD-2 and LCN-2 serum levels were not elevated in full-blown AS versus healthy controls (p=0.572, p=0.562, respectively). Therefore, these markers were not further determined in the SPACE cohort.
Conclusion
None of the candidate serum inflammatory markers were useful as diagnostic markers in the early phase of axSpA.
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INTRODUCTION
Reliable diagnosis of axial spondyloarthritis (axSpA) in the earliest phases of the disease remains an important unmet medical need. Ample evidence indicates that 1) signs and symptoms of active disease are as severe in early disease as in full-blown disease, with similar impact on function and quality of life,1–3 and 2) active early axSpA can be effectively treated with non-steroidal anti-inflammatory drugs (NSAIDs) and/or tumor necrosis factor inhibitors (TNFi).4–6 Moreover, current treatments fail to significantly inhibit pathological new bone formation when started in full-blown disease;7–9 although awaiting formal proof, starting the same treatments in very early disease may also impact structural progression.10,11 Although the time between first symptoms and diagnosis of axSpA has already been significantly reduced over the last decade by a combination of early referral strategies and the use of MRI to image axial inflammation,12–16 it remains a challenge to further reduce the diagnostic delay and to reliably distinguish early back pain due to axSpA from other causes of back pain.17–19
One potential way to address this challenge is the use of serum inflammatory biomarkers. A couple of inflammatory biomarkers have been reported to be elevated in active full-blown axSpA. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are both acute-phase reactants which are elevated in active SpA and decrease upon effective treatment.20–23 Moreover, calprotectin (also called S100A8/A9), a calcium binding protein, is expressed and secreted during macrophage infiltration in SpA synovitis.24–26 Calprotectin was recently shown to be a good serum biomarker for treatment responses in proof-of-concept trials in SpA and to independently predict radiographic progression in axSpA.27,28 Despite their value at the group level, the value of these serum biomarkers for diagnosis of axSpA in patients with early back pain remains unknown as they are neither very sensitive (for example, only one third of patients with active ankylosing spondylitis (AS) have an elevated CRP)20,22 nor specific as they reflect inflammation (whatever the origin) rather than axSpA as such.
Besides these inflammatory biomarkers that were already extensively studied in AS, our recent literature review identified a few other potentially interesting serum biomarkers (M. Turina et al., submitted for publication). Lin et al.29 recently described that levels of interleukin-27 (IL-27), a heterodimeric cytokine composed of p28 and Epstein–Barr Virus-induced gene 3 (EBI3) which belongs to the IL-12 family, were elevated in full-blown AS when compared with healthy controls but this finding has not yet been confirmed in an independent study. Human beta defensin-2 (hBD-2) and lipocalin-2 (LCN-2) are two antimicrobial peptides which are up-regulated by IL-17 and are consistently found at elevated levels in serum of patients with active psoriasis and inflammatory bowel disease (IBD).30–35 Considering the central role of IL-17 in the pathophysiology of axSpA36–38 and the pathophysiological and clinical overlap of axSpA with psoriasis and IBD,39 these two biomarkers could also be of potential interest.
46 SERUM INFLAMMATORY MARKERS NOT IN EARLY SpA
Accordingly, the aim of the present study was to assess the biomarker value of established inflammatory serum markers (CRP, ESR, and calprotectin) as well as more exploratory biomarkers (IL-27, hBD-2, and LCN-2) for the diagnosis of axSpA in patients with early back pain.
METHODS
Patients and samples
Serum was collected from 350 individuals after obtaining written informed consent to participate to the studies as approved by the local Ethics Committees of the participating centers. Cohort 1 (SPondyloArthritis Caught Early [SPACE]) consisted of 310 individuals with ‘early’ back pain (defined as at least 3 and maximally 24 months) and an age of onset below 45 years, referred for early evaluation of potential AxSpA.40 Cohort 2 consisted of 21 established AS patients according to the modified New York (mNY) criteria; all patients were TNFi naïve.41 Full descriptions of these cohorts were reported previously.40,41 Finally, we also obtained serum from 19 healthy controls.
Serum inflammatory biomarkers
From cohort 1, serum CRP and ESR levels were determined by local laboratories. Serum calprotectin levels were determined by enzyme-linked immunosorbent assay (ELISA) (Hycult Biotech, Uden, the Netherlands) using a 1:60 dilution and according to the manufacturer’s protocol.27,28
From cohort 2 and the healthy controls, serum IL-27, hBD-2, and LCN-2 levels were determined by ELISA according to the manufacturer’s protocol (eBiosciences, San Diego, CA; Phoenix pharmaceuticals, Inc. Belmont CA; and Research & Diagnostic Systems, Inc. Minneapolis, respectively). The dilutions were 1:2, 1:50, and 1:50 respectively.
Statistical analysis
Data between groups were compared using Mann-Whitney U tests. P-values less than 0.05 were considered statistically significant. Data were presented as box plots (Tukey) indicating the median and interquartile ranges (IQR). Whiskers represent 1.5 IQR, black dots represent outliers. Statistical analyses were performed with SPSS V21.0 (SPSS Inc, Chicago, USA).
47
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RESULTS
The baseline characteristics of cohort 1 are shown in Table 1. Of note, 119 patients fulfilled the ASAS axSpA criteria (of which 36 fulfilled the imaging arm) and 191 did not fulfill the ASAS axSpA criteria.
CRP, ESR and calprotectin levels in early axSpA
We first assessed whether CRP, ESR, and calprotectin levels, known to be elevated in full-blown ankylosing spondylitis, were also elevated in patients with early back pain fulfilling the ASAS axSpA criteria.42 The median (IQR) levels of CRP (3.00 [3.00-8.00] mg/l versus 3.00 [3.00-6.00] mg/l, p=0.317) (Figure 1A) and ESR (8.50 [5.00-17.00] mm/hour versus 9.00 [2.75-14.00] mm/hour, p=0.208) (Figure 1B) were not significantly different between patients fulfilling and not fulfilling the ASAS axSpA criteria in the SPACE cohort. In contrast, calprotectin levels (294 [214-367] ng/ml versus 251 [196-339] ng/ml, p=0.01) were significantly higher in patients with early back pain fulfilling versus those not fulfilling the ASAS axSpA criteria (Figure 1C). However, the discriminating value of calprotectin at the individual level was low: using a cut off value for calprotectin at a specificity of 90.0%
7
C R P
A S A S + A S A S -0
1 02 03 04 05 06 07 08 0
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ur
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/hou
r
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ASAS+ imaging arm ASAS-0
200
400
600
800 *
ng/m
l
A
D
C B
F E
Figure 1. Serum levels of A, c-reactive protein (CRP), B, erythrocyte sedimentation rate (ESR), and C, calprotectin of cohort 1 (SPACE) with early back pain patients fulfilling the ASAS axial spondyloarthritis (axSpA) criteria (n=119) versus early back pain patients not fulfilling the ASAS axial SpA criteria (n=191); and serum levels of D, CRP, E, ESR, and F, calprotectin of cohort 1 (SPACE) with patients fulfilling the ASAS axSpA criteria according to the imaging arm (n=36) versus patients not fulfilling the ASAS axial SpA criteria (n=191). Boxplot (Tukey): Data are presented as median (interquartile range). Whiskers represent 1.5 IQR and black dots represent outliers. *p<0.05 by Mann-Whitney U test.
48 SERUM INFLAMMATORY MARKERS NOT IN EARLY SpA
(412.40 ng/ml), the sensitivity was 10.0% and the positive predictive value (PPV) 38.7%. The post-test probability of having axSpA is thus not increased in comparison with the pre-test probability (119 out of 310 or 38.4%).
CRP, ESR and calprotectin levels in the imaging arm of early axSpA
The ASAS criteria consist of an imaging and a clinical arm. The imaging arm can be fulfilled only if abnormal MRI (according to the ASAS/OMERACT definition) or X-ray of sacroiliiac (SI-) joints (according to mNY) abnormalities are visible, and since calprotectin is an independent marker for axial spinal progression it might better associate to the imaging arm of the ASAS criteria. Therefore, we conducted similar analyses in patients fulfilling the imaging arm (n=36) of the ASAS axSpA criteria versus those not fulfilling the criteria (n=191). Again, levels of CRP (4.00 [3.00-9.00] mg/l versus 3.00 [3.00-6.00] mg/l, p=0.175) (Figure 1D), and ESR (6.50 [4.250-19.00] mm/hour versus 9.00 [4.00-13.00] mm/hour, p=0.512) (Figure 1E) were not different between the early axSpA patients fulfilling the ASAS imaging arm and controls not fulfilling the ASAS criteria (Figure 1D and E). Levels of calprotectin (313 [237-371] ng/ml versus 253 [195-338] ng/ml, p=0.01) were significantly higher in early back pain patients fulfilling the imaging arm of the ASAS axSpA criteria versus those not fulfilling the criteria (Figure 1F). As for the global axSpA group, however, the discriminatory value at the individual level was low. Using again a cut off for calprotectin at the 90% specificity level (249.95 ng/ml) as example, the PPV was 80% but the sensitivity was only 7.7%.
IL-27, hBD-2 and LCN-2 in full-blown AS versus healthy controls
As CRP, ESR, and calprotectin were not useful as diagnostic biomarkers for axSpA in the SPACE cohort, we explored the potential value of three additional potential biomarkers. To this purpose, we first assessed their serum levels in established active AS (cohort 2) versus controls. IL-27 was undetectable in all but one serum samples of AS and healthy controls (data not shown). Serum levels of hBD-2 (median and IQR: 2.61 [0.00-8.93] ng/ml versus 0.00 [0.00-26.65] ng/ml, p=0.572) (Figure 2A) and LCN-2 (55.47 [38.14-66.30] ng/ml versus 51.82 [46.59-68.57] ng/ml, p=0.562) (Figure 2B) were clearly detectable but were not elevated in AS versus healthy controls. As none of the 3 makers was elevated in AS, we did not proceed with testing the serum levels in the early back pain (SPACE) cohort.
DISCUSSION
We set up this study to assess whether inflammatory serum biomarkers can contribute to the diagnosis of axSpA in individuals presenting with early back pain. A first important finding is that serum CRP levels and ESR are not elevated in patients with early axSpA versus patients with back pain from different origins, despite that fact that elevated CRP is one
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of the features included in the ASAS axSpA criteria. Accordingly, specificity, sensitivity, and PPV analyses did not allow discrimination between patients and controls (data not shown). Importantly, however, the value of CRP and ESR were assessed here in an univariate analysis as the aim was to identify biomarkers that can easily and reproducibly be used to screen patients with early back pain to diagnose axSpA early. Albeit CRP and ESR do not appear to be useful tools for this purpose, this does not imply that these markers cannot be useful in individual patient when combined with other SpA features in a multivariate approach.
A second interesting finding is that, in contrast to CRP and ESR, calprotectin levels were significantly increased in early axSpA versus controls with back pain. This finding is consistent with a series of previous studies suggesting that calprotectin may slightly outperform CRP as marker of tissue inflammation in SpA,26–28,43 potentially because this protein is released during infiltration of myeloid cells in tissues and may thus more directly reflect some of the pathological processes in SpA. However, the difference in serum calprotectin levels detected at the group level between early axSpA and controls was not robust enough in terms of sensitivity and specificity to translate in a useful discriminative tool to identify axSpA patients. These findings are consistent with studies on other serum inflammatory markers including IL-6,44,45 alpha-2-macroglobulin,46 MMP-3,47–50 and PTX-3,51 which have been explored already in established axSpA but were not robust enough to apply in a diagnostic setting in early axSpA.
The lack of increase in serum levels of inflammatory biomarkers in axSpA versus controls is likely related to two issues. First, these biomarkers do not reflect a SpA-specific process but rather inflammation in general and therefore lack specificity. Intercurrent infections or the presence of another chronic inflammatory disease may lead to elevated CRP, ESR, and/or calprotectin in patients with mechanical back pain. One way to circumvent this issue would be to measure factors that are more specifically related to the immunopathology
1
hBD-2
AS Healthy Controls0
50
100
150ng
/ml
LCN-2
AS Healthy Controls0
50
100
150
ng/m
l
A B
Figure 2. Serum levels of A, human beta defensin-2 (hBD-2) and B, lipocalin-2 (LCN-2) in active full-blown ankylosing spondylitis (AS, n=21) versus healthy controls (n=19). Data are presented as median (interquartile range). Boxplot (Tukey): Data are presented as median (interquartile range). Whiskers represent 1.5 IQR and black dots represent outliers. *P<0.05 by Mann-Whitney U test. *p<0.05 by Mann-Whitney U test.
50 SERUM INFLAMMATORY MARKERS NOT IN EARLY SpA
of axSpA, such as biomarkers reflecting the activation of the IL-23/IL-17 axis. Despite their value in psoriasis and IBD, however, the IL-17-driven antimicrobial peptides hBD-2 and LCN-2 were not elevated in axSpA. This might be due to the fact that these peptides are mainly produced by epithelial cells, including keratinocytes and gut epithelial cells, and that IL-17 may act on different cell types in axSpA. Further investigations in the mechanistic aspects of SpA immunopathology remain warranted to identify novel potential biomarkers.
A second reason for the absence of elevated serum levels of inflammatory markers such as CRP and ESR may be the fact that inflammation is restricted to specific tissue compartments and does not extend to the systemic circulation and/or lymphoid organs in SpA. This concept is supported by the facts that a) in the present study a majority of early axSpA patients have CRP and ESR levels within the normal range despite active disease (n=171, 55.2%), b) even in the subset of patients with positive MRI imaging demonstrating active inflammation in the SI joints, CRP, ESR, and calprotectin levels were not further increased, and c) also in established SpA with active disease CRP levels are elevated in only one-third of the patients.20–23 Accordingly, we previously focused our research on the immunopathology of affected tissues, such as the synovial membrane, and found striking and reproducible alterations which, however, were not reflected in the peripheral blood compartment.52,53 If this concept is correct, the search for diagnostic markers should probably be focused on non-invasive measurements of tissue pathology (including MRI, PET-CT, and other types of molecular imaging) rather than on serum biomarkers.
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REFERENCES
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2. Wallis D, Haroon N, Ayearst R, Carty A, Inman RD. Ankylosing spondylitis and nonradiographic axial spondyloarthritis: part of a common spectrum or distinct diseases? J Rheumatol 2013;40(12):2038–41.
3. Boonen A, Sieper J, van der Heijde D, et al. The burden of non-radiographic axial spondyloarthritis. Semin Arthritis Rheum 2015;44(5):556–62.
4. Van Den Bosch F, Kruithof E, Baeten D, et al. Randomized double-blind comparison of chimeric monoclonal antibody to tumor necrosis factor alpha (infliximab) versus placebo in active spondylarthropathy. Arthritis Rheum 2002;46(3):755–65.
5. Braun J, Brandt J, Listing J, et al. Treatment of active ankylosing spondylitis with infliximab: a randomised controlled multicentre trial. Lancet 2002;359(9313):1187–93.
6. Sieper J, van der Heijde D, Dougados M, et al. Efficacy and safety of adalimumab in patients with non-radiographic axial spondyloarthritis: results of a randomised placebo-controlled trial (ABILITY-1). Ann Rheum Dis 2013;72(6):815–22.
7. Van der Heijde D, Landewé R, Einstein S, et al. Radiographic progression of ankylosing spondylitis after up to two years of treatment with etanercept. Arthritis Rheum 2008;58(5):1324–31.
8. Van der Heijde D, Salonen D, Weissman BN, et al. Assessment of radiographic progression in the spines of patients with ankylosing spondylitis treated with adalimumab for up to 2 years. Arthritis Res Ther 2009;11(4):R127.
9. Van der Heijde D, Landewé R, Baraliakos X, et al. Radiographic findings following two years of infliximab therapy in patients with ankylosing spondylitis. Arthritis Rheum 2008;58(10):3063–70.
10. Maas F, Spoorenberg A, Brouwer E, et al. Spinal radiographic progression in patients with ankylosing spondylitis treated with TNF-α blocking therapy: a prospective longitudinal observational cohort study. PLoS One 2015;10(4):e0122693.
11. Maksymowych WP, Zheng Y, Wichuk S, Chiowchanwisawakit P, Lambert RG. The effect of TNF inhibition on radiographic progression in ankylosing apondylitis: An observational cohort study of 384 patients. Ann Rheum Dis 2015;74(Suppl2): 123.
12. Brandt HC, Spiller I, Song I-H, Vahldiek JL, Rudwaleit M, Sieper J. Performance of referral recommendations in patients with chronic back pain and suspected axial spondyloarthritis. Ann Rheum Dis 2007;66(11):1479–84.
13. Poddubnyy D, Vahldiek J, Spiller I, et al. Evaluation of 2 screening strategies for early identification of
patients with axial spondyloarthritis in primary care. J Rheumatol 2011;38(11):2452–60.
14. Van Hoeven L, Vergouwe Y, de Buck PDM, Luime JJ, Hazes JMW, Weel AE a M. External Validation of a Referral Rule for Axial Spondyloarthritis in Primary Care Patients with Chronic Low Back Pain. PLoS One 2015;10(7):e0131963.
15. Rudwaleit M, Jurik a G, Hermann K-G a, et al. Defining active sacroiliitis on magnetic resonance imaging (MRI) for classification of axial spondyloarthritis: a consensual approach by the ASAS/OMERACT MRI group. Ann Rheum Dis 2009;68(10):1520–7.
16. Rudwaleit M, Khan M a, Sieper J. The challenge of diagnosis and classification in early ankylosing spondylitis: do we need new criteria? Arthritis Rheum 2005;52(4):1000–8.
17. Feldtkeller E, Khan MA, van der Heijde D, van der Linden S, Braun J. Age at disease onset and diagnosis delay in HLA-B27 negative vs. positive patients with ankylosing spondylitis. Rheumatol Int 2003;23(2):61–6.
18. Sorensen J, Hetland ML. Decreases in diagnostic delay are supported by sensitivity analyses. Ann Rheum Dis 2014;73(7):e45–e45.
19. Salvadorini, F. Bandinelli, A. Delle Sedie, L. Riente, A. Candelieri, S. Generini, N. Possemato, S. Bombardieri MM-C. Ankylosing spondylitis: how diagnostic and therapeutic delay have changed over the last six decades. Clin Exp Rheumatol 2012;30(4):561–5.
20. Benhamou M, Gossec L, Dougados M. Clinical relevance of C-reactive protein in ankylosing spondylitis and evaluation of the NSAIDs/coxibs’ treatment effect on C-reactive protein. Rheumatology (Oxford) 2010;49(3):536–41.
21. Visvanathan S, Wagner C, Marini JC, et al. Inflammatory biomarkers, disease activity and spinal disease measures in patients with ankylosing spondylitis after treatment with infliximab. Ann Rheum Dis 2008;67(4):511–7.
22. De Vries MK, van Eijk IC, van der Horst-Bruinsma IE, et al. Erythrocyte sedimentation rate, C-reactive protein level, and serum amyloid a protein for patient selection and monitoring of anti-tumor necrosis factor treatment in ankylosing spondylitis. Arthritis Rheum 2009;61(11):1484–90.
23. Poddubnyy D a, Rudwaleit M, Listing J, Braun J, Sieper J. Comparison of a high sensitivity and standard C reactive protein measurement in patients with ankylosing spondylitis and non-radiographic axial spondyloarthritis. Ann Rheum Dis 2010;69(7):1338–41.
24. Kane D, Roth J, Frosch M, Vogl T, Bresnihan B, FitzGerald O. Increased perivascular synovial membrane expression of myeloid-related proteins in psoriatic arthritis. Arthritis Rheum 2003;48(6):1676–85.
25. Kruithof E, De Rycke L, Vandooren B, et al. Identification of synovial biomarkers of response to
52 SERUM INFLAMMATORY MARKERS NOT IN EARLY SpA
experimental treatment in early-phase clinical trials in spondylarthritis. Arthritis Rheum 2006;54(6):1795–804.
26. De Rycke L, Baeten D, Foell D, et al. Differential expression and response to anti-TNFalpha treatment of infiltrating versus resident tissue macrophage subsets in autoimmune arthritis. J Pathol 2005;206(1):17–27.
27. Turina MC, Yeremenko N, Paramarta JE, De Rycke L, Baeten D. Calprotectin (S100A8/9) as serum biomarker for clinical response in proof-of-concept trials in axial and peripheral spondyloarthritis. Arthritis Res Ther 2014;16(5):413.
28. Turina MC, Sieper J, Yeremenko N, et al. Calprotectin serum level is an independent marker for radiographic spinal progression in axial spondyloarthritis. Ann Rheum Dis 2014;73(9):1746–8.
29. Lin T-T, Lu J, Qi C-Y, et al. Elevated serum level of IL-27 and VEGF in patients with ankylosing spondylitis and associate with disease activity. Clin Exp Med 2014;15(2):227-231.
30. Gambichler T, Bechara FG, Scola N, Rotterdam S, Altmeyer P, Skrygan M. Serum levels of antimicrobial peptides and proteins do not correlate with psoriasis severity and are increased after treatment with fumaric acid esters. Arch Dermatol Res 2012;304(6):471–4.
31. Jansen P a M, Rodijk-Olthuis D, Hollox EJ, et al. Beta-defensin-2 protein is a serum biomarker for disease activity in psoriasis and reaches biologically relevant concentrations in lesional skin. PLoS One 2009;4(3):e4725.
32. Kamata M, Tada Y, Tatsuta a, et al. Serum lipocalin-2 levels are increased in patients with psoriasis. Clin Exp Dermatol 2012;37(3):296–9.
33. Romaní J, Caixàs A, Ceperuelo-Mallafré V, et al. Circulating levels of lipocalin-2 and retinol-binding protein-4 are increased in psoriatic patients and correlated with baseline PASI. Arch Dermatol Res 2013;305(2):105–12.
34. Oikonomou KA, Kapsoritakis AN, Theodoridou C, et al. Neutrophil gelatinase-associated lipocalin (NGAL) in inflammatory bowel disease: association with pathophysiology of inflammation, established markers, and disease activity. J Gastroenterol 2012;47(5):519–30.
35. Yeşil A, Gönen C, Senateş E, et al. Relationship between neutrophil gelatinase-associated lipocalin (NGAL) levels and inflammatory bowel disease type and activity. Dig Dis Sci 2013;58(9):2587–93.
37. Baeten D, Baraliakos X, Braun J, et al. Anti-interleukin-17A monoclonal antibody secukinumab in treatment of ankylosing spondylitis: a randomised, double-blind, placebo-controlled trial. Lancet 2013;382(9906):1705–13.
38. Baraliakos X, Borah B, Braun J, et al. Long-term effects of secukinumab on MRI findings in relation to clinical efficacy in subjects with active ankylosing spondylitis:
an observational study. Ann Rheum Dis 2015;207544.
39. Dougados M, Baeten D. Spondyloarthritis. Lancet 2011;377(9783):2127–37.
40. Van den Berg R, de Hooge M, van Gaalen F, Reijnierse M, Huizinga T, van der Heijde D. Percentage of patients with spondyloarthritis in patients referred because of chronic back pain and performance of classification criteria: experience from the Spondyloarthritis Caught Early (SPACE) cohort. Rheumatology (Oxford) 2013;52(8):1492–9.
41. Salinas GF, De Rycke L, Barendregt B, et al. Anti-TNF treatment blocks the induction of T cell-dependent humoral responses. Ann Rheum Dis 2013;72(6):1037–43.
42. Sieper J, Rudwaleit M, Baraliakos X, et al. The Assessment of SpondyloArthritis international Society (ASAS) handbook: a guide to assess spondyloarthritis. Ann Rheum Dis 2009;68 Suppl 2:ii1–44.
43. Kruithof E, De Rycke L, Roth J, et al. Immunomodulatory effects of etanercept on peripheral joint synovitis in the spondylarthropathies. Arthritis Rheum 2005;52(12):3898–909.
44. Gratacós J, Collado A, Filella F, et al. Serum cytokines (IL-6, TNF-alpha, IL-1 beta and IFN-gamma) in ankylosing spondylitis: a close correlation between serum IL-6 and disease activity and severity. Br J Rheumatol 1994;33(10):927–31.
45. Pedersen SJ, Hetland ML, Sørensen IJ, Ostergaard M, Nielsen HJ, Johansen JS. Circulating levels of interleukin-6, vascular endothelial growth factor, YKL-40, matrix metalloproteinase-3, and total aggrecan in spondyloarthritis patients during 3 years of treatment with TNFα inhibitors. Clin Rheumatol 2010;29(11):1301–9.
46. Surrall K, Bird H, Dixon J. Caeruloplasmin , prealbumin and u2-macroglobulin as potential indices of disease activity in different arthritides. Clin Rheumatol 1987;(3):64–9.
47. Yang C, Gu J, Rihl M, et al. Serum levels of matrix metalloproteinase 3 and macrophage colony-stimulating factor 1 correlate with disease activity in ankylosing spondylitis. Arthritis Rheum 2004;51(5):691–9.
48. Maksymowych WP, Landewé R, Conner-Spady B, et al. Serum matrix metalloproteinase 3 is an independent predictor of structural damage progression in patients with ankylosing spondylitis. Arthritis Rheum 2007;56(6):1846–53.
49. Vandooren B, Kruithof E, Yu DTY, et al. Involvement of matrix metalloproteinases and their inhibitors in peripheral synovitis and down-regulation by tumor necrosis factor alpha blockade in spondylarthropathy. Arthritis Rheum 2004;50(9):2942–53.
50. Chen C-H, Lin K-C, Yu DTY, et al. Serum matrix metalloproteinases and tissue inhibitors of metalloproteinases in ankylosing spondylitis: MMP-3 is a reproducibly sensitive and specific biomarker of disease activity. Rheumatology (Oxford) 2006;45(4):414–20.
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51. Deban L, Jaillon S, Garlanda C, Bottazzi B, Mantovani A. Pentraxins in innate immunity: lessons from PTX3. Cell Tissue Res 2011;343(1):237–49.
52. Noordenbos T, Yeremenko N, Gofita I, et al. Interleukin-17-positive mast cells contribute to synovial inflammation in spondylarthritis. Arthritis Rheum 2012;64(1):99–109.
53. Yeremenko N, Noordenbos T, Cantaert T, et al. Disease-specific and inflammation-independent stromal alterations in spondylarthritis synovitis. Arthritis Rheum 2013;65(1):174–85.
Clinical and imaging signs of spondyloarthritis
in first-degree relatives of HLA-B27 positive
ankylosing spondylitis patients: the pre-
spondyloarthritis (Pre-SpA) cohort
Maureen C. Turina,1*, Janna J. de Winter 1*, Jaqueline E. Paramarta1, Mihaela Gamala1, Nataliya Yeremenko1,2, Marita N.
Nabibux3, Robert Landewé1, Dominique L. Baeten1,2
1Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology
and immunology Center, Academic Medical Center/University of Amsterdam,
Amsterdam, The Netherlands; 2Department of Experimental Immunology, Academic Medical Center/University of
Amsterdam, Amsterdam, The Netherlands;3Department of Rheumatology, Tergooi Hospital, Hilversum, The Netherlands
*Equal contributions
Submitted for publication
4
56 Pre-SpA INCEPTION COHORT
ABSTRACT
Objective
To investigate if seemingly healthy first-degree relatives (FDRs) of ankylosing spondylitis (AS) patients have clinical, laboratory or imaging features of spondyloarthritis (SpA).
Methods
FDRs of HLA-B27 positive AS patients between 18-40 years were included in Pre-SpA, a prospective inception cohort study. Clinical, biological and imaging data were obtained. FDRs were classified according to several sets of SpA classification criteria.
Results
We report baseline features of 51 FDRs included in this study. Twenty-nine (57%) FDRs had back pain; 2 (4%) had psoriasis, and none had other extra-articular manifestations. Three (6%) FDRs had low grade sacroiliitis, 1 (2%) had cervical syndesmophytes on X-ray, and 11 (22%) had bone marrow edema on MRI of the sacroiliiac joints. Seventeen of 51 (33%) FDRs fulfilled SpA classification criteria: 7 (14%) both the ASAS axSpA and ESSG criteria, 6 (12%) only the ASAS axSpA, and 4 (8%) only the ESSG criteria. None fulfilled other SpA classification criteria. FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria had more frequently (inflammatory) back pain and had a higher level of disease activity. No difference in inflammatory parameters, peripheral and extra-articular disease and HLA-B27 presence was found. Six (16%) of the FDRs not fulfilling the ASAS axSpA and/or ESSG classification criteria had imaging abnormalities suggestive of SpA.
Conclusion
A substantial proportion of seemingly healthy FDRs of HLA-B27 positive AS patients have clinical and/or imaging abnormalities suggestive of SpA. Thirty-three percent could be classified as SpA. Further follow-up will show which FDRs will develop clinically manifest SpA.
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INTRODUCTION
A major feature of spondyloarthritis (SpA) is its insidious onset and slow progression of signs and symptoms as well as of structural damage.1 This leads to a significant diagnostic delay of five to ten years.2-4 More recently, the development of referral strategies for early inflammatory back pain (IBP)5-7 and the use of magnetic resonance imaging (MRI) to visualize active sacroiliitis have probably decreased this diagnostic delay. However, detecting the earliest phases of the disease remains challenging, which has three potentially important implications. First, the absence of an early diagnosis delays adequate treatment of signs and symptoms of inflammation for several months to years. Second, uncontrolled early disease may initiate osteoproliferation, a process seemingly resistant to treatment in the later phases.8-10 And third, when the earliest phase of the disease is ignored, a comprehensive chronological and hierarchical mapping of all cellular and molecular mechanisms that drive SpA is illusive.11,12
Similar to rheumatoid arthritis, SpA might have a subclinical phase of disease preceding the clinical established phase, where abnormalities are present but clinical symptoms are lacking. A systematic screening and meticulous follow-up of those that are at high risk of developing SpA may help to address such challenges. Models explaining the genetic susceptibility to ankylosing spondylitis (AS), the prototypical axial form of SpA, suggest an 8% recurrence risk in first-degree relatives (FDRs) of AS patients.13 The comparison of familial and sporadic cases of AS suggest a higher familial aggregation of AS in patients with HLA-B27 positivity.14 Accordingly, several studies have suggested a 10-12% recurrence risk of AS (as defined by the presence of radiographic sacroiliitis) in FDRs of AS patients, with a twofold higher risk in HLA-B27 positive individuals.15-18 Other SpA subtypes were also frequently observed in FDRs of probands with AS or SpA.18,19
The fact that all these cross-sectional studies consistently show that FDRs of HLA-B27 positive AS patients have a strongly increased risk of developing SpA, opens the venue for systematic and detailed characterization of the earliest phases of SpA by prospective analysis of such FDRs at risk. In order to better detect, understand, and eventually treat the earliest phases of disease, the purpose of the present inception cohort study is to prospectively study the appearance and development of clinical, biological and imaging (X-ray and MRI) features of SpA in seemingly healthy FDRs of AS patients. We report here the baseline analysis of clinical and imaging features in 51 FDRs included in the study.
58 Pre-SpA INCEPTION COHORT
PATIENTS AND METHODS
Study design
Pre-SpA is an ongoing, prospective five-year inception cohort study. FDRs of HLA-B27 positive AS patients were included, between the ages of 18 and 40 years since new onset of SpA after the age of 45 years is rare and since the major objective is to study the development rather than the incidence of SpA. We selected probands with established AS rather than SpA as a whole spectrum for 3 reasons. 1) We aimed for a high entry-threshold by only including HLA-B27 positive AS patients, thereby avoiding as much misdiagnosed probands as possible, 2) the other genetic risk factors besides HLA-B27 have largely only been established in AS and not in other SpA subtypes,20 and 3) HLA-B27 positive patients tend to have more ankylosis than HLA-B27 negative patients,21 thereby possibly favoring the presence and detection of structural radiographic changes in FDRs. All participants signed informed consent prior to any study procedures. Major exclusion criteria were the presence of already diagnosed SpA, other rheumatic conditions including fibromyalgia, and back pain due to other conditions, such as intervertebral disc degeneration. All study procedures were done in compliance with the Helsinki Declaration. The study protocol was approved by the Medical Ethics Committee of the Academic Medical Center/University of Amsterdam.
Clinical evaluation at baseline
Data on demographics (gender, age, and race), medical and family history, and the use of medication were recorded. History specific for SpA-related features included back pain, IBP as defined by the Assessment of SpondyloArthritis international Society (ASAS) criteria,22
peripheral arthritis, enthesitis, dactylitis, psoriasis, inflammatory bowel disease (IBD), and uveitis, all objectified by a physician. Disease activity was measured by physician’s global assessment of disease activity (PhGA), patient’s global assessment of disease activity (PGA) on a visual analogue score (VAS), by patient’s nocturnal pain VAS, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and by Ankylosing Spondylitis Disease Activity Score-CRP (ASDAS-CRP). Function was assessed by the Bath Ankylosing Spondylitis Functional Index (BASFI). Clinical examination included a 68-tender and a 66-swollen joint count (TJC and SJC), an enthesitis score (Maastricht Ankylosing Spondylitis Enthesitis Score (MASES)), a dactylitis evaluation, the linear Bath Ankylosing Spondylitis Metrology Index (BASMI), chest expansion, and occiput-to-wall distance.22 Cut-off values of modified Schober and chest expansion were set at 4.5 cm and 3.6 cm respectively.23
Biological evaluation at baseline
Laboratory assessments included HLA-B27 testing, C-reactive protein (CRP) serum levels, and erythrocyte sedimentation rate (ESR). Levels of calprotectin were determined by enzyme-
59
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linked immunosorbent assay (ELISA) as indicated by the manufacturer (Hycult Biotech, the Netherlands).24,25
Imaging evaluation at baseline
Radiographs of the lumbar and cervical spine and of the sacroiliac joints (SIJs) were obtained. Anteroposterior X-rays of the SIJs were scored according to the modified New York (mNY) criteria.26 Lateral and anteroposterior X-rays of the lumbar and cervical spine were scored according to the modified Stoke AS Spine Score (mSASSS).27 MRIs were performed on a 3.0 tesla scanner (Philips Medical Systems, Best, The Netherlands), with sagittal T-1 weighted and short tau inversion recovery (STIR) sequences with a slice thickness of 4 mm for the spine (sagittal) and the SIJs (semicoronal). Both X-rays and MRIs were scored by one experienced, blinded reader (RL) for the presence of bone marrow edema (BME), according to the ASAS/OMERACT definition of a positive MRI.28
Analysis
Clinical, biological and imaging features of SpA were reported descriptively. Apart from missing imaging data of one FDR, data were complete. FDRs were classified according to the ASAS classification criteria for axial SpA (axSpA),29 the ASAS peripheral SpA criteria,30 the European Spondyloarthropathy Study Group (ESSG) criteria,31 the Amor criteria,32 the ClASsification criteria for Psoriatic ARthritis (CASPAR),33 and the mNY criteria.26 The proportion of FDRs fulfilling any SpA classification criteria was compared to that of FDRs not fulfilling SpA classification criteria by using the chi-square test. For continuous data Mann Whitney-U test was used. Data were presented as numbers and percentages or as mean and standard deviation (SD). Statistical tests were 2-sided and P-values less than 0.05 were considered statistically significant. A similar analysis was performed for FDRs with imaging signs suggestive of SpA versus FDRs without imaging abnormalities.
RESULTS
Clinical and biological features of SpA in FDRs of HLA-B27 positive AS patients
Fifty-one FDRs from 38 probands (comprising 33 parents and 5 siblings) with AS were included in this analysis. Main reasons to refuse study participation were abroad residencies, being too busy, fear for blood collection, and a few FDRs were not interested to participate without clarifying their motivation. The mean (SD) age at inclusion was 25 (5) years; 25 (49%) participants were male, and 26 (51%) were HLA-B27 positive. The baseline characteristics of the study population are summarized in Table 1. Twenty-nine (57%) FDRs reported back pain after inquiry, and 11 (22%) fulfilled the IBP criteria. Of the 51 FDRs, 20 (40%) reported
60 Pre-SpA INCEPTION COHORT
Table 1. Clinical characteristics, laboratory and imaging results of the FDRs of those fulfilling and not fulfilling the ASAS axSpA and/or ESSG classification criteria
Study population
Fulfilling the ASAS axSpA and/or ESSG criteria
Fulfilling vs not fulfilling the ASAS axSpA and/or ESSG criteria
ImagingLow grade sacroiliitis on X-ray 3 (6) 3 (18) 0 (0) 0.014Syndesmophytes of the lumbar spine on X-ray 0 (0) 0 (0) 0 (0)
-Syndesmophytes of the cervical spine on X-ray 1 (2) 0 (0) 1 (3) 0.473
Inflammatory lesions of the SIJ on MRI 11 (22) 7 (41) 4 (12) 0.020
Inflammatory lesions of the spine on MRI
0 (0) 0 (0) 0 (0)-
ASAS, Assessment of SpondyloArthritis international Society; ASDAS, Ankylosing Spondylitis Disease Activity Score; AxSpA, axial spondyloarthritis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Metrology Index; BMI, body mass index; cm, centimeter; CRP, c-reactive protein; DMARD, disease modifying antirheumatic drugs; ESR, erythrocyte sedimentation rate; ESSG, European Spondyloarthropathy Study Group; IBD, inflammatory bowel disease; HLA-B27, human leukocyte antigen-B27; kg, kilogram; MASES, Maastricht Ankylosing Spondylitis Enthesitis Score; m, meter; mm, millimeter; MRI, magnetic resonance imaging; NSAIDs, non-steroidal anti-inflammatory drugs; PGA patient global assessment of disease activity; PhGA, physician global assessment of disease activity; SD, standard deviation; SIJ, sacroiliac joints; SJC, swollen joint count; SpA, spondyloarthritis; TJC, tender joint count; TNF, tumor necrosis factor; VAS, visual analogue score. Data presented as n (%) unless otherwise specified.
62 Pre-SpA INCEPTION COHORT
past or present arthralgia, 1 (2%) reported past or present peripheral arthritis. None of the FDRs reported past or present enthesitis or dactylitis. Of all 51 FDRs, 2 (4%) had psoriasis, 1 (2%) reported IBD, no FDR reported past or present urethritis/diarrhea, and 1 (2%) had past or present uveitis. A modified Schober of <4.5 cm was found in 11 (22%) FDRs, and 2 (4%) FDRs had a chest expansion of <3.6 cm. None of the FDRs had arthritis but 8 (16%) had at least one tender joint. Ten (20%) participants had tenderness of at least one entheseal point, but none had dactylitis, nail psoriasis, or skin psoriasis. Laboratory results showed an elevated CRP, ESR or calprotectin in 6 (12%), 4 (8%) and 0 (0%) of the FDRs, respectively.
Imaging features of SpA in FDRs of HLA-B27 positive AS patients
Three (6%) FDRs had low-grade sacroiliitis not fulfilling the mNY criteria (grade I uni- or bilaterally, or grade II unilaterally) on X-ray, and 1 (2%) FDR had syndesmophytes on spinal X-ray. MRI showed inflammatory lesions of the SIJ, and spine in 11 (22%), and 0 (0%) of the FDRs, respectively (Figure 1).
Application of SpA classification criteria to FDRs of HLA-B27 positive AS patients
Seventeen (33%) FDRs fulfilled any of the SpA classification criteria at baseline: 7 (14%) fulfilled both the ASAS axSpA and the ESSG criteria, 6 (12%) only fulfilled the ASAS axSpA, and 4 (8%) only fulfilled the ESSG criteria. Of these 17 FDRs, 3 (6%) FDRs also fulfilled the Amor criteria. None of the FDRs fulfilled the ASAS peripheral SpA criteria, the CASPAR, or the mNY criteria.
When comparing FDRs fulfilling with those not fulfilling the ASAS axSpA and/or ESSG classification criteria (Table 1), back pain (17 (100%) vs. 12 (35%), p<0.001) and IBP (11 (65%) vs. 0 (0%), p<0.001) were more prevalent in the former group. Good response to non-steroidal anti-inflammatory drugs (NSAIDs) was also more prevalent in the group of FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria compared to those who did not (5 (29%) vs. 0 (0%), p=0.001). Furthermore, FDRs who fulfilled the ASAS axSpA and/or ESSG classification criteria had a higher number of tender entheseal points, and showed a trend to have more tender joints when compared with those not fulfilling the ASAS axSpA and/or ESSG classification criteria (7 (41%) vs. 3 (9%), p=0.007 and 5 (29%) vs. 3 (9%), p=0.059, respectively). In contrast, there were no differences in peripheral and extra-articular disease (past or present) between both groups. The group fulfilling the ASAS axSpA and/or ESSG classification criteria had a higher mean (SD) PhGA (12 (3) vs. 4 (9) mm, p<0.001), a higher VAS for patient’s nocturnal pain (13 (22) vs. 2 (3) mm; p=0.003), a higher BASDAI (2.04 (1.42) vs. 0.73 (1.00), p<0.001), and a higher ASDAS-CRP (0.67 (0.59) vs. 0.27 (0.38), p=0.007), with a trend towards a higher PGA (15 (18) vs. 8 (15) mm, p=0.065). The BASFI was worse in the FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria (0.85 (1.08) vs. 0.22 (0.46), p=0.001). FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria had low overall disease activity scores: only three FDRs had a BASDAI >4 and/or ASDAS-CRP >1.3.
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Inflammatory serum markers were not increased in FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria. However, BME on MRI (7 (41%) vs. 4 (12%), p=0.020) and signs of sacroiliitis on X-ray (3 (18%) vs. 0 (0%), p=0.014) were found more often in those fulfilling the ASAS axSpA and/or ESSG classification criteria.
Concluding, FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria had more axial, entheseal, and joint pain which was reflected in higher disease activity and worse function than those not fulfilling the ASAS axSpA and/or ESSG classification criteria. Except for BME
Figure 1. Images of cervical syndesmophytes on lateral X-ray (A) and a representative image of bone marrow edema on the magnetic resonance imaging of the sacroiliac joints (MRI SIJ) in the STIR sequences (B).
A
B
64 Pre-SpA INCEPTION COHORT
on MRI, however, they did not show objective signs of inflammation such as clinical arthritis or elevated acute phase response.
Comparison of FDRs with and without imaging abnormalities
Interestingly, 6 of 38 (16%) FDRs not fulfilling the ASAS axSpA and/or ESSG classification criteria had imaging abnormalities suggestive of SpA: One FDR had syndesmophytes on the cervical spine X-ray, and 5 FDRs had BME on MRI of the SIJ (Table 1 and Figure 1). Therefore, we conducted an analysis of all FDRs with imaging abnormalities (the group fulfilling the ASAS axSpA and/or ESSG classification criteria and the group without symptoms but with imaging abnormalities) versus those without imaging abnormalities. However, there were no differences in demographics, history of SpA symptoms, family history, disease activity, clinical examination, and laboratory findings between these two groups (Table 2).
Comparison of HLA-B27 positive versus HLA-B27 negative FDRs
Previous studies have shown that SpA mainly manifests in HLA-B27 positive FDRs.13,18 Therefore, we performed another analysis comparing the HLA-B27 positive FDRs with the HLA-B27 negative FDRs. Nevertheless, there were no differences found between these groups in demographics, history of SpA symptoms, disease activity, clinical examination, laboratory and imaging data (Table 3).
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Table 2. Clinical characteristics, laboratory and imaging results of the FDRs with and without imaging abnormalities on X-ray and/or MRI of the SIJ and spine
Imaging abnormalities Yes (n= 12) No (n= 38) p-value
Demographics Male gender 6 (50) 19 (50) -Caucasian 12 (100) 37 (98) 0.574Age, years, mean (SD) 26.75 (5.88) 25.45 (5.06) 0.480BMI, kg/m2, mean (SD) 23.92 (3.91) 23.31 (2.90) 0.667HLA-B27 positive 6 (50) 19 (50) -Current smoker 3 (25) 11 (29) 0.910Use of DMARD, TNF inhibitors or corticosteriods ever 0 (0) 0 (0) -
History Axial disease Back pain 8 (67) 21 (65) 0.490Inflammatory back pain 3 (25) 8 (21) 0.776Buttock pain 0 (0) 2 (5) 0.416Good response to NSAIDs 3 (25) 2 (5) 0.049
ImagingLow grade sacroiliitis on X-ray 2 (8) 1 (4) 0.556SpA abnormalities of the lumbar spine on X-ray 0 (0) 0 (0) -Syndesmophytes of the cervical spine on X-ray 1 (4) 0 (0) 0.997Inflammatory lesions of the SIJ on MRI 6 (24) 5 (20) 0.735Inflammatory lesions of the spine on MRI 0 (0) 0 (0) -
ASAS, Assessment of SpondyloArthritis international Society; ASDAS, Ankylosing Spondylitis Disease Activity Score; axSpA, axial spondyloarthritis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Metrology Index; BMI, body mass index; CASPAR, ClASsification criteria for Psoriatic ARthritis; cm, centimeter; CRP, c-reactive protein; DMARD, disease modifying antirheumatic drugs; ESSG, European Spondyloarthropathy Study Group; ESR, erythrocyte sedimentation rate; FDR, first degree relatives; IBD, inflammatory bowel disease; HLA-B27, human leukocyte antigen-B27; kg, kilogram; MASES, Maastricht Ankylosing Spondylitis Enthesitis Score; m, meter; mm, millimeter; mNY, modified New York; MRI, magnetic resonance imaging; NSAIDs, non-steroidal anti-inflammatory drugs; PGA patient global assessment of disease activity; PhGA, physician global assessment of disease activity; SD, standard deviation; SIJ, sacroiliiac joints; SJC, swollen joint count; SpA, spondyloarthritis; TJC, tender joint count; TNF, tumor necrosis factor; VAS, visual analogue score. Data presented as n (%) unless otherwise specified.
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DISCUSSION
We report here the baseline demographic, clinical, laboratory, and imaging features of 51 individuals included in a prospective inception cohort study of FDRs of HLA-B27 positive AS patients. This study aims to investigate the earliest, pre-clinical phases of disease based on the concept that FDRs of HLA-B27 positive AS patients have a significantly increased risk to develop SpA.
A first major conclusion is that at baseline 33% of FDRs have clinical and/or imaging features that allow a classification of SpA according to the ASAS axSpA and/or ESSG classification criteria. These findings are perfectly in line with previous cross-sectional studies showing an increased SpA risk among FDRs. Remarkably, the recurrence rate in our study (33%) is even higher than in the reported studies (4.9-12% recurrence), while the mean age in our study was lower.13,18,34 Several factors may contribute to this higher recurrence rate. First, FDRs having clinical symptoms could be more willing to participate in our study than FDRs without symptoms, which may lead to channeling bias. Indeed, a substantial percentage of ‘seemingly healthy’ FDRs reported back pain when actively questioned for this symptom at baseline. The fact that these FDRs were not investigated for or diagnosed with axial SpA before inclusion in the study may be related either to the fact that the back pain symptoms were relatively mild or to ignorance of general physicians for these alarm symptoms. Second, we have defined SpA in this study using ASAS axSpA, ESSG, Amor, CASPAR, and mNY criteria whereas previous studies mostly used the mNY criteria. It is now well recognized that AS, defined by the mNY criteria, represents only a fraction of the total SpA spectrum. Supporting this explanation, none of the FDRs fulfilled the mNY criteria. Third, inclusion of MRI may have led to increased classification of FDRs. However, in our study only 2 out of 17 FDRs would not have been classified without MRI.35,36
In our study we classified FDRs according to the ASAS axSpA and/or ESSG classification criteria and did not diagnose SpA based on the rheumatologist’s opinion for several reasons. First, there are no diagnostic criteria for SpA. Second, a diagnosis based on expert’s opinion is subjective and has large intra- and inter-observer variation and therefore is not feasible in this cohort. A potential drawback of using SpA classification criteria, however, is that the a priori probability of fulfilling the ASAS axSpA, ESSG and/or Amor criteria is higher in these FDRs than in populations used to develop these criteria,29,35,37 because the study design implies that all participants have a positive family history and that half of them are HLA-B27 positive. Nevertheless, the fact that FDRs fulfilling the ASAS axSpA and/or ESSG classification criteria had significantly higher scores for disease activity than those not fulfilling the ASAS axSpA and/or ESSG classification criteria adds to the rightness of using these criteria for this particular study design.
Importantly, some key features of SpA including the presence of peripheral disease or
70 Pre-SpA INCEPTION COHORT
extra-articular manifestations and increased inflammatory parameters were only rarely observed in FDRs and were also not different in those fulfilling the ASAS axSpA and/or ESSG classification criteria versus those who did not. Again, we cannot entirely exclude a selection bias here as we recruited ‘seemingly healthy’ FDRs and as axial symptoms may be more frequently unrecognized by FDRs and physicians than peripheral or extra-articular disease. Alternatively, this observation may suggest that axial disease precedes other SpA manifestations during disease development. Strikingly, 6 out of 38 (16%) FDRs not fulfilling the ASAS axSpA and/or ESSG classification criteria had imaging abnormalities suggestive for SpA, with one showing cervical syndesmophytes and 5 depicting sacroiliac BME on MRI. Moreover, we did observe abnormalities on the MRI SIJ but did not observe spine abnormalities on MRI. These individuals did not have any other clinical or biological signs of SpA. These imaging abnormalities might represent the subclinical phase. Future follow-up will learn if and which of these FDRs will evolve into the clinically established phase of SpA. We will be able to address the relevance of these observations in the near future by a) extending the cohort size which will allow to replicate the current findings, and b) prospective follow-up of these FDRs, especially focusing on those with imaging abnormalities only. A key question is whether these imaging abnormalities predict clinical signs and symptoms of SpA. A possibility is that a positive MRI, even when ‘highly suggestive of axial SpA’ is a feature that can be observed more frequently in ‘normal individuals’ than previously thought. Alternatively, part of the MRI abnormalities may indeed be the first signs of yet subclinical axial SpA.
Another intriguing finding was that 9 of 17 (53%) FDRs fulfilling SpA classification criteria were HLA-B27 negative, of whom 1 fulfilled both the ASAS axSpA and ESSG criteria, an additional 4 the ASAS axSpA and an additional 4 fulfilled the ESSG criteria. This proportion is higher than in earlier reports on FDRs (14-43%) in AS and non-radiographic axSpA,35,36,38 which indicated a lower recurrence risk in HLA-B27 negative FDRs. This could be due to the relative size of the current study. However, if confirmed in a larger sample set, further follow-up of these FDRs will allow us to determine if FDRs showing signs and symptoms of SpA will evolve to more active and severe disease, independently of HLA-B27 status or, alternatively, if the presence of HLA-B27 may promote exacerbation and persistence of subclinical pathology. Moreover, we could determine if genetic factors such as SNPs in ERAP-1 and IL-23R may have a bigger contribution in the development of SpA than previously thought.
In conclusion, the data from this cohort suggest that a substantial proportion of FDRs of HLA-B27 positive AS patients between the age of 18-40 years do have clinical signs and symptoms and/or imaging abnormalities suggestive for SpA. Accordingly, 33% could already be classified as SpA. Extension of the sample size and follow-up of all subjects will allow us to disentangle the sequence of events that may lead to clinically manifest SpA and will allow us to determine which initial features may predict such a development.
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REFERENCES
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2. Feldtkeller E, Khan MA, van der Heijde D, van der Linden S, Braun J. Age at disease onset and diagnosis delay in HLA-B27 negative vs. positive patients with ankylosing spondylitis. Rheumatol Int 2003;23:61-6.
3. Salvadorini G, Bandinelli F, Delle Sedie A, Riente L, Candelieri A, Generini S, et al. Ankylosing spondylitis: how diagnostic and therapeutic delay have changed over the last six decades. Clin Exp Rheumatol 2012;30:561-5.
4. Sorensen J, Hetland ML. Decreases in diagnostic delay are supported by sensitivity analyses. Ann Rheum Dis 2014;73:e45.
5. Brandt HC, Spiller I, Song IH, Vahldiek JL, Rudwaleit M, Sieper J. Performance of referral recommendations in patients with chronic back pain and suspected axial spondyloarthritis. Ann Rheum Dis 2007;66:1479-84.
6. Poddubnyy D, Vahldiek J, Spiller I, Buss B, Listing J, Rudwaleit M, et al. Evaluation of 2 screening strategies for early identification of patients with axial spondyloarthritis in primary care. J Rheumatol 2011;38:2452-60.
7. Sieper J, Srinivasan S, Zamani O, Mielants H, Choquette D, Pavelka K, et al. Comparison of two referral strategies for diagnosis of axial spondyloarthritis: the Recognising and Diagnosing Ankylosing Spondylitis Reliably (RADAR) study. Ann Rheum Dis 2013;72:1621-7.
8. van der Heijde D, Landewe R, Baraliakos X, Houben H, van Tubergen A, Williamson P, et al. Radiographic findings following two years of infliximab therapy in patients with ankylosing spondylitis. Arthritis Rheum 2008;58:3063-70.
9. van der Heijde D, Landewe R, Einstein S, Ory P, Vosse D, Ni L, et al. Radiographic progression of ankylosing spondylitis after up to two years of treatment with etanercept. Arthritis Rheum 2008;58:1324-31.
10. van der Heijde D, Salonen D, Weissman BN, Landewe R, Maksymowych WP, Kupper H, et al. Assessment of radiographic progression in the spines of patients with ankylosing spondylitis treated with adalimumab for up to 2 years. Arthritis Res Ther 2009;11:R127.
12. Yeremenko N, Paramarta JE, Baeten D. The interleukin-23/interleukin-17 immune axis as a promising new target in the treatment of spondyloarthritis. Curr Opin Rheumatol 2014;26:361-70.
13. Brown MA, Laval SH, Brophy S, Calin A. Recurrence risk modelling of the genetic susceptibility to ankylosing spondylitis. Ann Rheum Dis 2000;59:883-6.
14. Joshi R, Reveille JD, Brown MA, Weisman MH, Ward MM, Gensler LS, et al. Is there a higher genetic load
of susceptibility loci in familial ankylosing spondylitis? Arthritis Care Res (Hoboken) 2012;64:780-4.
15. Moller P, Vinje O, Dale K, Berg K, Kass E. Family studies in Bechterew’s syndrome (ankylosing spondylitis). II. Prevalences of symptoms and signs in relatives of HLAB27 negative probands. Scand J Rheumatol 1984;13:11-4.
16. van der Linden SM, Valkenburg HA, de Jongh BM, Cats A. The risk of developing ankylosing spondylitis in HLA-B27 positive individuals. A comparison of relatives of spondylitis patients with the general population. Arthritis Rheum 1984;27:241-9.
17. Vinje O, Dale K, Moller P. Radiographic evaluation of patients with Bechterew’s syndrome (ankylosing spondylitis) and their first-degree relatives. Findings in the spine and sacro-iliac joints and relations to non-radiographic findings. Scand J Rheumatol 1985;14:119-32.
18. Dernis E, Said-Nahal R, D’Agostino MA, Aegerter P, Dougados M, Breban M. Recurrence of spondylarthropathy among first-degree relatives of patients: a systematic cross-sectional study. Ann Rheum Dis 2009;68:502-7.
19. Chou CT, Lin KC, Wei JC, Tsai WC, Ho HH, Hwang CM, et al. Study of undifferentiated spondyloarthropathy among first-degree relatives of ankylosing spondylitis probands. Rheumatology (Oxford) 2005;44:662-5.
20. Reveille JD. The genetic basis of spondyloarthritis. Ann Rheum Dis 2011;70 Suppl 1:i44-50.
21. Ramiro S, Stolwijk C, van Tubergen A, van der Heijde D, Dougados M, van den Bosch F, et al. Evolution of radiographic damage in ankylosing spondylitis: a 12 year prospective follow-up of the OASIS study. Ann Rheum Dis 2015;74:52-9.
22. Sieper J, Rudwaleit M, Baraliakos X, Brandt J, Braun J, Burgos-Vargas R, et al. The Assessment of SpondyloArthritis international Society (ASAS) handbook: a guide to assess spondyloarthritis. Ann Rheum Dis 2009;68 Suppl 2:ii1-44.
23. Ramiro S, van Tubergen A, Stolwijk C, van der Heijde D, Royston P, Landewe R. Reference intervals of spinal mobility measures in normal individuals: the mobility study. Ann Rheum Dis 2014.
24. Turina MC, Sieper J, Yeremenko N, Conrad K, Haibel H, Rudwaleit M, et al. Calprotectin serum level is an independent marker for radiographic spinal progression in axial spondyloarthritis. Ann Rheum Dis 2014;73:1746-8.
25. Turina MC, Yeremenko N, Paramarta JE, De Rycke L, Baeten D. Calprotectin (S100A8/9) as serum biomarker for clinical response in proof-of-concept trials in axial and peripheral spondyloarthritis. Arthritis Res Ther 2014;16:413.
26. van der Linden S, Valkenburg HA, Cats A. Evaluation of diagnostic criteria for ankylosing spondylitis. A proposal
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for modification of the New York criteria. Arthritis Rheum 1984;27:361-8.
27. Creemers MC, Franssen MJ, van’t Hof MA, Gribnau FW, van de Putte LB, van Riel PL. Assessment of outcome in ankylosing spondylitis: an extended radiographic scoring system. Ann Rheum Dis 2005;64:127-9.
28. Rudwaleit M, Jurik AG, Hermann KG, Landewe R, van der Heijde D, Baraliakos X, et al. Defining active sacroiliitis on magnetic resonance imaging (MRI) for classification of axial spondyloarthritis: a consensual approach by the ASAS/OMERACT MRI group. Ann Rheum Dis 2009;68:1520-7.
29. Rudwaleit M, van der Heijde D, Landewe R, Listing J, Akkoc N, Brandt J, et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis 2009;68:777-83.
30. Rudwaleit M, van der Heijde D, Landewe R, Akkoc N, Brandt J, Chou CT, et al. The Assessment of SpondyloArthritis International Society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general. Ann Rheum Dis 2011;70:25-31.
31. Dougados M, van der Linden S, Juhlin R, Huitfeldt B, Amor B, Calin A, et al. The European Spondylarthropathy Study Group preliminary criteria for the classification of spondylarthropathy. Arthritis Rheum 1991;34:1218-27.
32. Amor B, Dougados M, Mijiyawa M. [Criteria of the classification of spondylarthropathies]. Rev Rhum Mal Osteoartic 1990;57:85-9.
33. Taylor W, Gladman D, Helliwell P, Marchesoni A, Mease P, Mielants H, et al. Classification criteria for psoriatic arthritis: development of new criteria from a large international study. Arthritis Rheum 2006;54:2665-73.
34. J. DB, Polman A, de B-M. Hereditary factors in rheumatoid arthritis and ankylosing spondylitis. Ann Rheum Dis 1961;20:215-20.
35. Molto A, Paternotte S, Comet D, Thibout E, Rudwaleit M, Claudepierre P, et al. Performances of the Assessment of SpondyloArthritis International Society axial spondyloarthritis criteria for diagnostic and classification purposes in patients visiting a rheumatologist because of chronic back pain: results from a multicenter, cross-sectional study. Arthritis Care Res (Hoboken) 2013;65:1472-81.
36. Weber U, Hodler J, Jurik AG, Pfirrmann CW, Rufibach K, Kissling RO, et al. Assessment of active spinal inflammatory changes in patients with axial spondyloarthritis: validation of whole body MRI against conventional MRI. Ann Rheum Dis 2010;69:648-53.
37. van den Berg R, de Hooge M, van Gaalen F, Reijnierse M, Huizinga T, van der Heijde D. Percentage of patients with spondyloarthritis in patients referred because of chronic back pain and performance of classification criteria: experience from the Spondyloarthritis Caught Early (SPACE) cohort. Rheumatology (Oxford) 2013;52:1492-9.
38. Tomero E, Mulero J, de Miguel E, Fernandez-Espartero C, Gobbo M, Descalzo MA, et al. Performance of the
Assessment of Spondyloarthritis International Society criteria for the classification of spondyloarthritis in early spondyloarthritis clinics participating in the ESPERANZA programme. Rheumatology (Oxford) 2014;53:353-60.
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Calprotectin (S100A8/9) as serum biomarker
for clinical response in proof-of-concept trials
in axial and peripheral spondyloarthritis
Maureen C. Turina1, Nataliya Yeremenko1,2, Jacqueline E. Paramarta1, Leen De Rycke1,3, Dominique L. Baeten1,2
1Department of Clinical Immunology and Rheumatology, Academic Medical Center/
University of Amsterdam, Amsterdam, The Netherlands; 2Laboratory of Experimental Immunology, Academic Medical Center/University of
Amsterdam, Amsterdam, the Netherlands; 3Department of Rheumatology and Clinical Immunology, University Medical Center
Utrecht, Utrecht, The Netherlands
Arthritis Res Ther. 2014;16(5):413.
5
76 CALPROTECTIN IN PoC TRIALS
ABSTRACT
Introduction
Biomarkers complementing clinical evaluations may help to reduce the length and size of proof-of-concept (PoC) trials aimed to obtain quick go or no-go decisions in the clinical development of new treatments. We aimed to identify and validate serum biomarkers with a high sensitivity to change upon effective treatment in spondyloarthritis (SpA) PoC trials.
Methods
The candidate biomarkers high sensitive-C-reactive protein (hs-CRP), interleukin-6 (IL-6), pentraxin-3 (PTX-3), alpha-2-macroglobulin (alpha-2-MG), matrix metalloproteinase-3 (MMP-3), calprotectin, and vascular endothelial growth factor (VEGF) were determined by enzyme-linked immunosorbent assay (ELISA) in healthy controls (n=20) and SpA patients before and after 2 weeks of infliximab (n=18) or placebo (n=19) treatment in cohort 1. Clinical outcome was evaluated at week 12. Results were validated in ankylosing spondylitis (AS) with infliximab (cohort 2, n=21) and peripheral SpA with etanercept (cohort 3, n=20).
Results
Serum levels of calprotectin, hs-CRP, PTX-3, VEGF (all p<0.001) and MMP-3 (p=0.062), but not IL-6 and alpha-2-MG, were increased in SpA versus healthy controls. Treatment with infliximab, but not placebo, significantly decreased calprotectin (p<0.001) and hs-CRP (p<0.001) levels, with a similar trend for MMP-3 (p=0.063). The Standardized Response Mean (SRM), which reflects the ability to detect changes over time, was high for calprotectin (-1.26), good for hs-CRP (-0.96) and moderate for MMP-3 (-0.52). Calprotectin and hs-CRP, but not MMP-3, were good biomarkers for treatment response in axial and peripheral SpA as evaluated and confirmed in cohort 2 and 3, respectively.
Conclusions
Calprotectin and hs-CRP are good serum biomarkers with high sensitivity to change upon effective treatment at the group level in small-scale, short-term PoC trials in SpA.
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INTRODUCTION
The use of tumor necrosis factor (TNF) blockers has dramatically improved the clinical outcome and quality of life of patients with spondyloarthritis (SpA). Originally implemented in ankylosing spondylitis (AS) and psoriatic arthritis (PsA), there is now increasing evidence that they are equally effective in other subtypes such as non-radiographic axial SpA and non-AS, non-PsA peripheral SpA.1-6 Nevertheless, TNF blockade in SpA still has important limitations. First, contra-indications and side effects, especially in patients with severe comorbidity, preclude the use of TNF blockers in a significant proportion of SpA patients. Second, TNF blockade fails to fully control signs and symptoms of disease in a significant proportion of patients, with only 15 to 20% reaching partial remission.1-6 Third, the currently available evidence suggests that TNF blockade fails to halt new bone formation and ankylosis.7 Finally, TNF blockade fails to induce long-lasting drug-free remission as disease relapses within a few months of treatment interruption in a large majority of patients.8,9
These limitations indicate that there is still an important unmet medical need for alternative treatment options in SpA. However, the success of TNF blockade also raises important medical and ethical hurdles to perform large, long-term, placebo-controlled trials with novel drugs. Additional strategies to obtain quick go and no-go signals in small short-term proof-of-concept (PoC) trials before proceeding to large long-term clinical studies are thus required. Such tools may comprise biomarkers which reliably show high sensitivity to change upon clinical response at the group level. A biomarker is a ‘characteristic that can be objectively measured and evaluated as an indicator of a normal biologic process, a pathophysiologic process, or a pharmacologic response to a therapeutic intervention’.10 If sensitive and reproducible, changes in biomarker levels during treatment may thus help to substantiate a genuine effect on specific biological processes in PoC trials.
Several biomarkers have previously been directly or indirectly associated with treatment response in SpA. C-reactive protein (CRP) is known to be elevated in active disease and to decrease upon effective treatment in SpA, but is less useful than in rheumatoid arthritis (RA) as two thirds of the SpA patients have normal CRP levels.11-14 Interleukin-6 (IL-6) is the main driver of CRP; serum IL-6 levels are significantly increased in active SpA and decrease upon clinical response after TNF blockade.15,16 Whereas CRP belongs to the short pentraxins, the pentraxin family also contains long pentraxins, including pentraxin-3 (PTX-3), which have been proposed as biomarkers of inflammation.17 Alpha-2-macroglobulin (alpha-2-MG) is another CRP-independent acute phase response protein that is used as serum biomarker.18
Besides acute phase response proteins, several potential biomarkers have been identified based on their involvement in the immunopathology of SpA. Matrix metalloproteinase-3 (MMP-3) levels are associated with peripheral arthritis, disease activity, progression of structural damage and response to TNF inhibition in SpA.19-21 Calprotectin, a heterodimer
78 CALPROTECTIN IN PoC TRIALS
consisting of S100A8 and S100A9 (previously called myeloid-related protein [MRP] 8 and 14, respectively), is expressed and secreted during monocyte infiltration into inflamed tissues, including macrophage infiltration in SpA synovitis.22-24 Calprotectin serum levels are elevated in SpA, correlate well with disease activity and decrease upon TNF blockade.23 Finally, SpA synovitis is characterized by pronounced hypervascularity,25,26 which is at least in part mediated by vascular endothelial growth factor (VEGF). VEGF serum levels are elevated and correlate well with inflammation and disease activity in SpA.27,28
In this study, we aimed to systematically assess the value of these serum proteins as biomarkers of effective treatment in PoC trials with TNF blockers in SpA. More specifically, we aimed to identify which of these serum proteins can best discriminate between anti-TNF treatment and placebo as early as 2 weeks after start of treatment.
METHODS
Patients and samples
Serum samples and clinical data for 20 healthy controls (HCs) and 78 SpA patients fulfilling the European Spondylarthropathy Study Group (ESSG)29 criteria were retrieved from our arthritis biobank for this analysis according to the study protocol as approved by the Medical Ethics Committee of the Academic Medical Center/University of Amsterdam (2013_057). The SpA population consisted of 3 separate cohorts, where cohort 2 and 3 are considered as independent validation cohorts. Cohort 1 consisted of 18 SpA patients with AS (n=8), PsA (n=8) and undifferentiated spondyloarthritis (USpA) (n=2), who received infliximab (5 mg/kg intravenously) and 19 SpA patients with AS (n=9), PsA (n=9) and USpA (n=1), who received placebo at week 0, 2 and 6.1 Cohort 2 consisted of 21 patients with AS according to the modified New York criteria, treated with infliximab (5mg/kg intravenously) at week 0, 2 and 6.30 Cohort 3 consisted of 20 peripheral SpA patients treated with etanercept (25 mg subcutaneously bi-weekly).31 None of the patients had been previously treated with a TNF blocker. Serum was obtained at baseline and week 2 for the first two cohorts, and at baseline and week 4 for cohort 3. The complete description of these cohorts and the response to treatment was reported previously.1, 30, 31
Serum biomarkers
We determined the serum levels of the following candidate biomarkers by enzyme-linked immunosorbent assay (ELISA) as indicated by the manufacturers: high-sensitivity (hs)-CRP (Research & Diagnostic Systems, Inc. Minneapolis), IL-6 (Research & Diagnostics Systems, Inc. Minneapolis), PTX-3 (Research & Diagnostic Systems, Inc.), alpha-2-MG (Abcam, Cambridge, UK), MMP-3 (Biotrak, Amersham Pharmacia Biotech, Buckinghamshire, UK), VEGF (Research
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& Diagnostics Systems, Inc.), and calprotectin (Hycult Biotech, the Netherlands). All assays were performed in duplicate.
Statistical analysis
Data were represented as mean (standard error of the mean) and compared using the parametric t-test (paired where appropriate) using the GraphPad Prism software program version 5.01. A p-value below 0.05 was considered as statistically significant. The standardized response mean (SRM) was calculated as the mean change in a parameter in a defined period of time divided by the standard deviation (SD) of that change. An SRM below 0.5, between 0.5 and 0.8, and above 0.8 indicates a poor, moderate and good potential to detect changes over time, respectively.32 Power calculations to attain 90% power with a significance level of 0.05 were performed using the nQuery Advisor version 7.0 software program.
RESULTS
Baseline serum biomarkers in SpA versus HCs
We first assessed which serum biomarkers were increased in active SpA compared to HCs using the baseline samples of cohort 1 (Figure 1), assuming that serum biomarkers that are increased in active disease could potentially be modulated and normalized by effective treatment. We thus used this strategy to select biomarkers of interest; it was not the aim to identify markers with a high diagnostic discriminative capacity between SpA and HCs. The serum levels of hs-CRP (16.44±2.36 µg/ml versus 0.84±0.27 µg/ml, p<0.001), PTX-3 (271.4 ± 35.0 pg/ml versus 46.0±23.6 pg/ml, p<0.001), calprotectin (1.76±0.13 µg/ml versus 0.65±0.10 µg/ml, p<0.001) and VEGF (237.0±30.3 pg/ml versus 16.7±5.7 pg/ml, p<0.001) were significantly higher in active SpA versus HCs, with a similar trend for MMP-3 (0.96±0.21 µg/ml versus 0.29±0.04 µg/ml, p=0.062). In contrast, levels of alpha-2-MG and IL-6 were not significantly different between active SpA and HCs. Elevated serum levels, defined as more than the mean + 2 SD of the serum levels of HCs, were observed in 86% of the SpA patients for calprotectin, 82% for VEGF, 81% for hs-CRP, 74% for MMP-3, and 59% for PTX-3.
Short-term modulation of serum biomarkers by infliximab in SpA
We next assessed which of these biomarkers were significantly downregulated by infliximab but not placebo treatment as early as two weeks after initiation of therapy. We previously reported that both arms of this cohort were well randomized for disease activity (as judged by parameters such as patient’s and physician’s global assessment of disease activity and Bath ankylosing spondylitis disease activity index (BASDAI), and that there was a significant decrease in these parameters during treatment with infliximab but not placebo.1 Serum
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levels of the investigated biomarkers were similar at baseline between the infliximab and placebo arms of cohort 1 (Figure 2). In the placebo group, none of the serum biomarkers changed significantly between baseline and week 2 (Figure 2). In contrast, we observed a significant decrease in serum levels of hs-CRP (p<0.001), IL-6 (p=0.047), and calprotectin
Figure 1. Serum biomarker levels in active spondyloarthritis (SpA) (n=37) versus healthy controls (HC) (n=20). Independent sample t-tests were performed. Data are represented as mean (standard error of the mean). *p<0.05. hs-CRP, high sensitive C-reactive protein; IL-6, interleukin-6; PTX-3, pentraxin-3; alpha-2-MG, alpha-2-macroglobulin; MMP-3, matrix metalloproteinase-3; VEGF, vascular endothelial growth factor.
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(p<0.001) after two weeks of infliximab treatment, with a similar trend for MMP-3 (p=0.063) (Figure 2). Levels of PTX-3, alpha-2-macroglobulin and VEGF were not significantly modulated by infliximab over this period.
Figure 2. Changes in serum biomarkers between baseline (week 0) and week 2 of infliximab (IFX) (n=18) versus placebo (PLC) (n=19) treatment in active SpA. Paired t-tests were performed. Data are represented as mean (standard error of the mean), *p<0.05. hs-CRP, high sensitive C-reactive protein; IL-6, interleukin-6; PTX-3, pentraxin-3; alpha-2-MG, alpha-2-macroglobulin; MMP-3, matrix metalloproteinase-3; VEGF, vascular endothelial growth factor.
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Potential of serum biomarkers to change sensitively upon active treatment in SpA
As the previous analyses identified calprotectin, hs-CRP, IL-6 and MMP-3 as the most promising biomarkers of treatment response, we next assessed their potential to change upon active treatment by using the SRM, which reflects the ability to detect changes over time.32 The SRM in the infliximab group was -1.26 for calprotectin, -0.96 for hs-CRP, -0.56 for IL-6, and -0.52 for MMP-3. In comparison, the SRM in the placebo group was -0.20 for calprotectin, -0.13 for hs-CRP, -0.05 for IL-6, and 0.23 for MMP-3. Thus, the delta SRM (SRM of active treatment minus SRM of placebo) was -1.06 for calprotectin, -0.83 for hs-CRP, -0.51 for IL-6, and -0.75 for MMP-3. As calprotectin and hs-CRP correlated moderately (r=0.648), we next aimed to confirm that an early change in calprotectin levels is superior to CRP as biomarker of clinically effective treatment by performing a power analysis on the data of cohort 1. Demonstration of a significant difference between infliximab and placebo treatment using changes in calprotectin levels over two weeks as outcome parameter with a power of 90% and a significance level of 0.05 would require 15 patients per group. A similar analysis with CRP would require 24 patients per group. Finally, we determined if a combination of changes in calprotectin and hs-CRP levels would be superior in treatment response compared to changes in calprotectin alone. Changes in calprotectin levels are independently associated to treatment response but when combining with changes to hs-CRP levels the association to treatment response was no longer significant.
Serum biomarkers of active treatment in AS
Cohort 1 consisted of different SpA subtypes, mainly AS and PsA. To ascertain that the biomarker findings are not biased by the SpA subtype and that the data can be extrapolated to more homogenous SpA study populations, we performed two additional sets of analysis. First, we reanalyzed the biomarker data of cohort 1 separately for AS (n=8 in the infliximab group and n=9 in the placebo group) and PsA (n=8 in the infliximab group and n=9 in the placebo group). In the AS group, only hs-CRP (p=0.006) and calprotectin (p=0.028) decreased significantly after two weeks of infliximab treatment (Figure 3A). Decreases in IL-6 and MMP-3 levels did not reach significance and none of the biomarkers changed in the placebo arm (data not shown). The SRM was -0.98 for calprotectin and -1.39 for hs-CRP. For PsA patients, only calprotectin (p=0.003) decreased significantly after two weeks of infliximab treatment, with a similar but non-significant trend for hs-CRP (p=0.071) (Figure 3B). None of the biomarkers changed in the placebo arm (data not shown). The SRMs in PsA patients were -1.58 for calprotectin and -0.75 for hs-CRP.
Second, we performed a similar biomarker analysis in an independent cohort of patients with AS without peripheral arthritis or enthesitis (n=20) receiving infliximab at week 0, 2 and 6 (cohort 2). As shown in Figure 3C, hs-CRP (p=0.001) and calprotectin (p=0.019) serum levels decreased significantly after two weeks of infliximab treatment. MMP-3 (p=0.093) showed a similar but non-significant trend in this cohort. The SRMs was -0.56 for calprotectin and
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-0.59 for hs-CRP. Taken together, these data indicate that changes in calprotectin and hs-CRP serum levels reflect well the response to active treatment with infliximab in AS.
Serum biomarkers of treatment response in peripheral SpA
The previous analyses suggest that there may be some differences in serum biomarkers between AS and PsA. To confirm and extend these data and to ascertain that these biomarkers do not only reflect response to infliximab but also other TNF inhibitors, we analyzed changes of serum biomarkers between baseline and week 4 of etanercept treatment in patient with peripheral SpA (cohort 3). As shown in Figure 4, we again observed a significant decrease in serum levels of calprotectin (p=0.032), hs-CRP (p=0.035) and MMP-3 (p=0.045). In this cohort, the SRMs were -0.55 for calprotectin, -0.54 for hs-CRP, and -0.51 for MMP-3. Furthermore, changes in calprotectin levels were not influenced by the presence of psoriasis.
Figure 3. Changes in serum biomarker levels between baseline (week 0) and week 2 of infliximab treatment in the ankylosing spondylitis (AS) patients (n=8) (A) and psoriatic arthritis (PsA) patients (n=8) (B) of cohort 1 as well as in the AS patients from cohort 2, who did not have peripheral disease (n=21) (C). Paired t-tests were performed. Data are represented as mean (standard error of the mean). *p<0.05. hs-CRP, high sensitive CRP; MMP-3, matrix metalloproteinase-3.
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Calprotectin as a biomarker in CRP-negative patients
Both calprotectin and CRP are not highly specific to SpA and are elevated in several diseases. In SpA, CRP levels are not elevated in two thirds of the patients. Furthermore, the correlation between CRP and calprotectin is modest in SpA (r=0.634), suggesting that calprotectin may provide more or additional information in comparison with CRP. We analyzed whether calprotectin is of additional value by determining the sensitivity to change upon treatment effect in CRP-negative patients. We therefore stratified for CRP status (positive or negative), using the threshold for normal values of our local laboratory.
For cohort 1, the delta calprotectin levels were -0.30±0.21 μg/ml in CRP-negative patients versus -0.90±0.13 μg/ml in CRP-positive patients, with a corresponding SRM of -0.79 and -1.60 in CRP-negative and CRP-positive patients, respectively. For cohort 2, the delta calprotectin levels were -0.19±0.14 μg/ml in CRP-negative patients versus -0.35±0.15 μg/ml in CRP-positive patients, with a corresponding SRM of -0.38 and -0.81 in CRP-negative and CRP-positive patients, respectively. For cohort 3, the delta serum calprotectin levels was -0.10±0.11 μg/ml in CRP-negative patients versus -0.30±0.18 μg/ml in CRP-positive patients, with a corresponding SRM of -0.35 and -0.66 in CRP-negative and CRP-positive patients, respectively.
DISCUSSION
Tissue inflammation is one of the major features of both axial and peripheral SpA but remains difficult to quantify and monitor in an objective and reliable way in clinical research. The most commonly used biomarkers for inflammation in SpA are magnetic resonance imaging (MRI) and CRP. MRI is able to visualize inflammatory lesions such as synovitis, enthesitis and bone marrow oedema in axial and peripheral SpA and these lesions decrease or even disappear upon effective treatment.33,34 Accordingly, MRI is now used as measure for inflammation in clinical trials in AS and axial SpA. However, even in patients with high
Figure 4. Changes in serum biomarkers between baseline (week 0) and week 4 of etanercept treatment (n=20) in peripheral SpA. Paired t-tests were performed. Data are represented as mean (standard error of the mean). *p<0.05. hs-CRP, high sensitive C-reactive protein; MMP-3, matrix metalloproteinase-3.
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clinical disease activity MRI scores are often low, which makes it difficult to detect significant pre- and post-treatment changes in small size PoC trials.35 The second widely used measure of inflammation in SpA is CRP. CRP levels do correlate at the group level with clinical disease activity, decrease upon effective treatment and are included in the ankylosing spondylitis disease activity score (ASDAS).36 As for MRI, however, an important issue is that baseline serum levels of CRP are elevated only in a fraction of patients with active SpA, hs-CRP may therefore perform better than classical CRP measurements.13,37
In the current study we explored the value of different candidate serum biomarkers of clinical response in SpA, thereby focusing on the specific situation of small, short-term PoC trials. We aimed to identify serum proteins that are significantly modulated by effective treatment with TNF blockers but not by placebo as early as 2 weeks after treatment initiation. In line with the previously discussed data, we found that hs-CRP is a useful biomarker of inflammation in this context as, despite not being elevated in all patients at baseline, it did rapidly and significantly decrease in both axial and peripheral SpA treated with either infliximab or etanercept. The high SRM and the absence of changes in the placebo-treated patients confirm its value as biomarker of inflammation in PoC trials. Interestingly, serum levels of IL-6, the major driver of CRP, did not appear to be a reliable marker of treatment response in our study. Moreover, two recent clinical trials with IL-6-receptor blockers failed to demonstrate clinical efficacy in AS.38,39 Taken together, these data suggest that, even though CRP may be used as biomarker, the IL-6-CRP axis is not a pivotal inflammatory pathway in SpA.
The major finding of the study is that serum levels of calprotectin appeared to be the most robust and reliable marker of treatment response in both axial and peripheral SpA, even outperforming hs-CRP in some analyses. For example, a power calculation in the infliximab cohort indicated that the use of calprotectin rather than hs-CRP as biomarker for inflammation would allow to a significant reduction in the size of the cohort. In contrast to CRP, there is also clear evidence that calprotectin directly reflects key inflammatory processes in SpA. Calprotectin is produced by myeloid cells and neutrophils and is secreted when these cells transmigrate through the endothelium to the inflamed tissues. Elevated levels of calprotectin as measured in synovial fluid in arthritis or in the faeces in inflammatory bowel disease thus reflect local tissue infiltration by myeloid cells.40,41 We and others have demonstrated that calprotectin is released locally in SpA synovitis, that the degree of synovial infiltration with myeloid cells and neutrophils reflect disease activity in peripheral SpA, and that effective treatment of peripheral SpA is associated with a rapid and robust decrease of calprotectin-positive cells in the inflamed synovium.22-24, 42 In contrast, much less is known about calprotectin expression in axial disease. Taken together, these data indicate that secretion of calprotectin may be a good reflection of local migration and activation of inflammatory innate immune cells in target tissues of SpA. Accordingly, a decrease in these calprotectin levels upon treatment is likely to reflect a genuine biological effect on chronic
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tissue inflammation.
Although we used only TNF blockers as effective drugs in the present study, we have now evidence that the biomarker value of calprotectin is not restricted to this sole mode of action. In a recent PoC study with the monoclonal anti-IL17A antibody, secukinumab, we demonstrated that both CRP and S100A8 and A9 levels decreased rapidly in the treated patients.35 Supporting the concept that calprotectin may have additive value compared to CRP, changes between baseline and week 6 levels of S100A8 and A9, but not CRP, correlated with assessment of spondyloarthritis 20 (ASAS20) and ASAS40 responses at week 6. Moreover, baseline levels of S100A8 and S100A9 but not CRP had a high sensitivity to change upon clinical response to treatment in this trial.
The combination of calprotectin and hs-CRP as biomarkers for clinical response, does not give any additional value compared to calprotectin alone. In contrast to calprotectin and hs-CRP, the other candidate biomarkers did not perform that well in our studies. In line with previous reports,16,20,28,43 serum levels of markers such as VEGF and MMP-3 did decrease upon effective anti-inflammatory therapy but the treatment effects were either smaller or less consistent across different SpA subtypes and cohorts in comparison with calprotectin and hs-CRP. This may also be due to the specific setting of the present study where we aimed to detect very early changes (at week 2) in biomarker levels.
It is important to emphasize here that our data certainly do not imply that serum biomarkers such as calprotectin or hs-CRP should replace clinical outcome parameters. Indeed, clinical outcomes (including composite indices such as BASDAI and ASDAS) can also show significant and rapid changes in anti-TNF treated patients. However, the correlation between a serum biomarker such as calprotectin and clinical outcomes such as BASDAI is significant but weak (r=0.325), indicating that both measures do not cover exactly the same aspects of the disease. Clinical outcome parameters may also be more sensitive to placebo responses and thus combination of clinical outcome measures with serum biomarkers may help to obtain a consistent picture which can support go or no-go decisions in proof-of-concept trials. A second aspect to emphasize is that calprotectin, similarly to CRP, is not exclusively elevated in SpA but also in many other inflammatory conditions.44 Co-morbidity may influence serum levels of calprotectin and CRP in SpA. Nevertheless, we demonstrated here that effective treatment still induces rapid, robust and consistent changes of these serum biomarkers which are not observed during placebo treatment.
Our study has two important limitations. First, we used a candidate approach based on a limited set of potential biomarkers emerging from literature and/or insights in tissue inflammation in SpA. However, a more systematic approach using proteomics or gene expression arrays allowing identification of novel biomarkers therefore certainly remains warranted. For example, an unbiased microarray analysis of peripheral blood cells could identify a set of genes which expression was closely correlated to disease activity in AS; one
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of these genes codes for LIGHT and serum levels of LIGHT were confirmed to correlate with CRP and erythrocyte sedimentation rate (ESR).45 Second, we focused on the use of serum biomarkers in a very specific setting, namely the measurement of a biological impact on inflammation in PoC trials. The set-up and size of the studies used in our analyses do not allow determination of whether changes in calprotectin and hs-CRP levels not only reflect treatment response at the group level but also allow to distinguish at the individual level responders from non-responders to TNF blockade. Moreover, it remains unknown if serum biomarkers such as calprotectin may also reflect other important clinical features of SpA. As, for example, both CRP and VEGF serum levels correlate with osteoproliferation in axial SpA,46,47 it would be interesting to explore the value of calprotectin in similar settings. Finally, we did not explore yet the value of calprotectin as biomarker of early disease, including non-radiographic axial SpA and patients presenting with early inflammatory back pain.
CONCLUSIONS
In summary, good biomarkers are needed in the development of novel therapies in SpA to provide quick go and no-go signals for PoC trials. Our data indicate that calprotectin and hs-CRP perform well as serum biomarkers as these biomarkers have a high sensitivity to change upon clinical effective treatment and could be of use in the development of new treatments.
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A psychometric analysis of outcome
measures in peripheral spondyloarthritis
Maureen C. Turina1*, Sofia Ramiro1 *, Dominique L. Baeten1, Philip Mease2, Jacqueline E. Paramarta1, In-Ho Song3, Aileen L.
Pangan3, Robert Landewé1
1Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology
and immunology Center, Academic Medical Center/University of Amsterdam,
Amsterdam, The Netherlands; 2Swedish Medical Center & University of Washington, Seattle, Washington, United
States;
3AbbVie Inc., North Chicago, Illinois, United States
*Equal contributions
Ann Rheum Dis. 2015 Aug 5;1–6
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ABSTRACT
Objectives
To assess the discriminatory capacity of various outcome measures and response criteria in patients with peripheral SpondyloArthritis (pSpA).
Methods
Data originated from two randomized controlled trials, ABILITY-2 and Tnf Inhibition in Peripheral SpondyloArthritis (TIPES). Continuous outcome measures included patient’s global assessment (PGA)/physician’s global assessment of disease (PhGA), C-reactive protein (CRP), tender joint counts (TJC)/swollen joint counts (SJC), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and the Ankylosing Spondylitis Disease Activity Score (ASDAS). Dichotomous response criteria included Peripheral SpondyloArthritis Response Criteria (PSpARC), American College of Rheumatology (ACR), ASDAS and BASDAI response criteria. The capacity to discriminate between adalimumab and placebo groups was assessed by standardised mean differences (SMD) for continuous variables, and Pearson’s χ2 for dichotomous response criteria.
Results
Within each trial, the composite indices for axial SpA assessment, ASDAS-CRP (SMD: -0.63 and -0.89 in ABILITY-2 and the TIPES trial, respectively) and BASDAI (SMD: –0.50 and -0.73), and the single-item measures PGA (SMD: -0.47 and -1.12) and PhGA (SMD: -0.64 and -0.87) performed better than other single-item measures, such as CRP (SMD: -0.18 and -0.53), SJC or TJC. In general, the PSpARC and ACR response criteria discriminated better than ASDAS and BASDAI response criteria.
Conclusions
The axial SpA-specific ASDAS-CRP and BASDAI, but also PGA and PhGA, demonstrated good discriminatory ability in patients with pSpA. The pSpA-specific pSpARC response criteria and the RA-specific ACR response criteria also discriminated well. To fully capture typical pSpA manifestations, it may be worth developing new pSpA-specific indices with better performance and face validity.
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INTRODUCTION
Spondyloarthritis (SpA) is a spectrum of diseases with several subtypes with overlapping clinical, radiographic and genetic characteristics.1 Recently, the Assessment in SpondyloArthritis international Society (ASAS) has developed classification criteria for SpA, based on the predominant clinical manifestation, as either axial SpA (axSpA), presenting with chronic back pain, or peripheral SpA (pSpA), presenting with arthritis, enthesitis or dactylitis.1,2 Several tumour necrosis factor inhibitors (TNFi) have been approved for axSpA (both non-radiographic axSpA (nr-axSpA) and Ankylosing Spondylitis (AS)), as well as for Psoriatic Arthritis (PsA), although not for pSpA.3-7 Two randomized controlled trials (RCTs) have been performed to assess the efficacy of TNFi in pSpA.8,9 Adalimumab (ADA) was effective in both trials, which had different primary endpoints because no composite measures or response criteria had been previously validated in patients with pSpA. In the ABILITY-2 trial, a new composite outcome measure, the Peripheral SpondyloArthritis Response Criteria (PSpARC)40, was developed as the primary endpoint.9 In the Tnf Inhibition in PEripheral SpondyloArthritis (TIPES) trial, the improvement in patient’s global assessment of disease (PGA) was chosen as the primary endpoint.8
Therefore, there exists a need to identify discriminant outcome measures for pSpA. Several efficacy variables were used in the two RCTs, including measures developed specifically for AS, such as the Ankylosing Spondylitis Diseases Activity Score (ASDAS) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI); and measures developed specifically for rheumatoid arthritis (RA, also applied in PsA), including the American College of Rheumatology (ACR)20/50/70. However, the performance of all these outcome measures in pSpA is unknown, and we hoped to determine which measures best reflect disease activity and clinical response, because the success of future therapeutic clinical trials depends not only on a well-defined patient population, but also on the availability of valid outcome measures and response criteria. Taking into account the Outcome Measures in Rheumatology Clinical Trials (OMERACT) guidance,10,11 we compared the discriminative properties of outcome measures in pSpA. The aim of this study was to assess the sensitivity to change and discriminatory aspects of outcome measures and response criteria in pSpA.
METHODS
Patient population
The analysis included data from two double-blind placebo (PBO)-controlled RCTs, ABILITY-2 and TIPES,8,9 which evaluated the efficacy and safety of ADA in active patients with pSpA. ABILITY-2 (NCT01064856) included patients fulfilling the ASAS pSpA criteria2 who did
94 ANALYSIS OF OUTCOME MEASURES IN pSpA
not have PsA or AS. The primary endpoint was PSpARC40 at week 12, defined as ≥40% improvement from baseline in PGA and patient global pain, and ≥40% improvement in any of the following: (1) swollen joint count (SJC) and tender joint count (TJC); (2) enthesitis count; or (3) dactylitis count.
The TIPES trial (EUDRACT 2008-006885-27) included patients with pSpA, fulfilling the European Spondyloarthropathy Study Group (ESSG) criteria and/or the Amor criteria,12,13 without PsA or AS. The primary endpoint was the change in PGA at week 12.
Outcome measures and response criteria
The performance of the following outcome measures in assessing disease activity and treatment response after 12 weeks was evaluated: PGA, patient global pain, physician’s global assessment of disease activity (PhGA), ASDAS-CRP, BASDAI, SJC, TJC and C-reactive protein (CRP).
The patient global pain in the past week, PGA, and PhGA of current disease activity were recorded on a 0-100 mm visual analogue scale (VAS). The ASDAS-CRP, originally developed for AS, includes questions pertaining to axial and peripheral symptoms, PGA and CRP.14 Disease activity was classified as follows: <1.3, inactive disease; 1.3 to <2.1, moderate disease; 2.1 to ≤3.5, high disease; and >3.5, very high disease.15 The BASDAI, also developed for AS, consists of questions mainly for axial and peripheral complaints, measured on a 0-10 cm VAS.
Clinical response criteria assessed were PSpARC40/50/70, ASDAS-major improvement (ASDAS-MI, change in ASDAS≥2.0), ASDAS-clinically important improvement (ASDAS-CII, change in ASDAS≥1.1), ASDAS-inactive disease (ASDAS-ID, ASDAS<1.3),15 BASDAI50 (improvement of ≥50% in BASDAI score), BASDAI ≥2 units (improvement of ≥2 units),16 and ACR20/50/70.
Since the TIPES trial did not capture patient global pain, enthesitis or dactylitis counts, a modified PSpARC40 was determined, which included 40% improvements from baseline in PGA, patient global pain and SJC66 and TJC68. Patient global pain was calculated as the mean of BASDAI components #3 (joint pain/swelling) and #4 (enthesitis), because these showed the highest correlation to patient global pain in the ABILITY-2 trial (Spearman’s coefficient=0.6). Modified ACR20/50/70 criteria were derived for the TIPES study, where patient global pain was calculated as above.
Statistical analysis
Analyses were performed for all outcome measures, for the two RCTs in the ‘as observed’ population, without imputation for rare missing data. The RCTs were separately analysed because this allowed results from one trial to be used to confirm results from the other, and
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also because there were differences in the outcome measures collected and the inclusion criteria.
First, we evaluated whether levels assessed by these measures could discriminate between two states of disease activity. Since no gold standard is available to define disease activity states in pSpA, patients (in each trial) were assigned to (arbitrarily determined) states of low disease activity and high disease activity based on the PhGA and PGA at baseline of treatment (<40 vs ≥60 mm, excluding patients with values in between, in order to increase separation). In subgroups with low disease activity and high disease activity, the standardised mean difference (SMD) was calculated as the difference between the group means divided by the pooled standard deviation (SD). The SMD has no units, which facilitates comparison across disease measures. An SMD with higher absolute value indicates better discriminatory ability.
For the continuous outcome measures, the sensitivity to change of each outcome measure for detecting improvement from baseline to week 12 was determined by comparing the adjusted standardised means of change from baseline to week 12 for all measures for both treatment groups separately. Adjusted standardised mean changes from baseline to week 12 were obtained for each continuous outcome measure (dependent), stratified for treatment (ADA and PBO) and adjusted for baseline values of the corresponding outcome measure (covariate), using analysis of co-variance (ANCOVA). The following formula was used for standardising: ‘disease activity outcome change (week 12-baseline) divided by SD of that outcome at baseline’. These standardised mean changes reflect sensitivity to change of an outcome measure within a treatment group (ADA vs PBO).
We then evaluated whether responses assessed by these measures could discriminate between ADA treatment and PBO treatment by determining SMDs, which reflect the capacity of continuous outcomes measures to discriminate between change under ADA and change under PBO. Furthermore, the t-score and the Guyatt’s effect size (ES) were determined for discriminatory capacity and sensitivity to change, respectively. Guyatt’s ES is the mean change in the treatment group divided by the SD of the PBO group, and relates the magnitude of the effect (the ‘signal’) to the magnitude of the non-specific change (the ‘noise’). Guyatt’s ES of 0.2, 0.5 and 0.8 represent small, medium and large effect size, respectively.17 A higher t-score indicates a better discriminatory ability within the same trial. The discriminatory ability of the dichotomous response criteria was determined by Pearson’s c2 (chi-square) or Fisher’s exact test (if n<5). With a constant number of observations per outcome measure, a higher c2 indicates better discriminatory ability. Analyses were performed using SPSS V.20 (SPSS, Chicago, Illinois, USA).
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RESULTS
Demographics and disease characteristics
In total, 205 patients were included: 165 from ABILITY-2 and 40 patients from the TIPES trial. The primary results have been reported previously.8,9 Patients with pSpA were more often female and the mean age was around 40 years. Half of them were HLA-B27 positive and the mean number of swollen joints was 5-6 (see online supplementary table S1). Of note, a high proportion had a history of enthesitis, and in ABILITY-2, dactylitis was not common. About half of them were using disease-modifying antirheumatic drugs (DMARDs), most often methotrexate or sulfasalazine, in equal proportions. Overall, the outcome measures were similar at baseline between the ADA and the PBO groups in both studies.
Discrimination between disease activity states
In the ABILITY-2 subgroups with low disease activity versus high disease activity at baseline based on PhGA, the SMD was highest for ASDAS-CRP (1.16) followed by BASDAI (1.13), patient global pain (1.03), and BASDAI #3 (1.00) (Table 1). In the TIPES trial, the SMD was highest for BASDAI #1 (2.66), PGA (2.01), ASDAS-CRP (1.84) and BASDAI (1.75). In the ABILITY-2 subgroups with low disease activity and high disease activity based on PGA, the SMD was highest for patient global pain (4.46) followed by ASDAS-CRP (2.08), BASDAI #4 (1.62) and BASDAI (1.61) (data not shown). In the TIPES trial, the SMD was highest for BASDAI (2.22) followed by ASDAS-CRP (2.18), patient global pain (1.89), and PhGA (1.71).
Sensitivity to change of continuous outcome measures
All measures showed an improvement after 12 weeks of treatment in both trials, with greater improvements observed in patients on ADA versus PBO treatment (Figure 1). Across both studies, the outcome measures with greatest sensitivity in detecting change from baseline after 12 weeks of treatment were PhGA, PGA, patient global pain, ASDAS-CRP, BASDAI and SJC. The ranking of the adjusted standardised means of change from baseline of the measures differed slightly between the trials. In ABILITY-2, the largest changes from baseline were observed in PhGA, patient global pain, PGA, and ASDAS-CRP. In the TIPES study, the largest changes from baseline were observed in ASDAS-CRP, PGA, PhGA and patient global pain.
Discriminatory aspects of continuous outcome measures
In ABILITY-2, PhGA had the highest SMD (-0.64), (as well as Guyatt’s ES and t-scores, data not shown), followed by ASDAS-CRP (-0.63), patient global pain (-0.50), BASDAI (-0.50), TJC78 (-0.50), and PGA (-0.47) (Table 2). In the TIPES trial, PGA had the highest SMD (-1.12), (and
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Table 1. Validation constructs: Discrimination between low disease activity and high disease activity according to physician’s global assessment (PhGA) at baseline
ABILITY-2 TIPESLow (<40)mean (SD)
n=15
High (≥60)mean (SD)
n=84
SMD Low (<40)mean (SD)
n=6
High (≥60)mean (SD)
n=12
SMD
PGA, 0-100 mm VAS 55.3 (17.0) 71.0 (15.7) 0.99 45.8 (13.4) 75.2 (15.1) 2.01Patient global pain, 0-100 mm VAS
aIn TIPES, SJC was 0-66 joints. bTJC 0-68 joints and patient global pain were derived from the mean of BASDAI #3 and #4.SD, standard deviation; SMD, standardised mean difference; #, number; VAS, visual analog scale; PGA, patient global assessment; PhGA, physician global assessment; ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score based on C-reactive protein; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; SJC, swollen joint count; TJC, tender joint count; CRP, C-reactive protein;
Guyatt’s ES and t-scores, data not shown), followed by patient global pain (-0.93); ASDAS-CRP (-0.89), PhGA (-0.87), some single-item components of BASDAI and BASDAI itself (-0.73). SJC discriminated well in the TIPES, but not the ABILITY-2 trial. Since the discriminatory performance of outcome measures had not been previously investigated in the pSpA population, the effects of level of low disease activity and high disease activity at baseline on performance were measured. The measures performed similarly, independently of level of disease activity at baseline (data not shown). However, in ABILITY-2, but not TIPES, the discriminatory ability of ASDAS-CRP, BASDAI, PGA, PhGA and TJC78 was enhanced in the subgroups with higher disease activity at baseline defined by BASDAI, compared to the subgroup with lower disease activity.
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-2.0
-1.5
-1.0
-0.5 0.0 0.5
PhGA
PGA
BASDAI
BASDAI #1
BASDAI #2
BASDAI #3
BASDAI #4
BASDAI #5
BASDAI #6
ASDAS-CRP
CRP
TJC 78
SJC 76
Patient global pain
-2.0
-1.5
-1.0
-0.5 0.0 0.5
PGA
PhGA
BASDAI
BASDAI #1
BASDAI #2
BASDAI #3
BASDAI #4
BASDAI #5
BASDAI #6
ASDAS-CRP
CRP
TJC 68
SJC 66
Patient global pain
adjusted standardized mean of change from baseline
ABILITY-2
TIPES
ADA PBO
Figure 1. Sensitivity to change of continuous outcome measures. Adjusted standardised mean changes from baseline for all outcome measures, adjusted for baseline values of variables. Outcomes are ranked independently for each trial in descending order based on the adjusted standardised means of change for the active treatment group. For TIPES, patient global pain was derived from the mean of BASDAI #3 and #4.
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Table 2. Discrimination of disease activity measurements between patients on ADA versus PBO
ABILITY-2 TIPESMean Δ from
BL ADA(SD), N=82
Mean Δ from BL PBO
(SD), N=81
SMD Mean Δ from BL ADA
(SD), N=19
Mean Δ from BL PBO
(SD), N=19
SMD
PGA, 0-100 mm VAS -28.0 (26.0)b -16.2 (24.5) d -0.47 -31.0(23.3)
a N=80, b N=81, c N=77, d N=80. e In TIPES, SJC was 0-66 joints, f In TIPES, TJC was 0-68 joints and patient global pain was derived from the mean of BASDAI #3 and #4. Δ, change; #, number; SD, standard deviation; SMD, standardised mean difference; BL, baseline; ADA, adalimumab; PBO, placebo; PGA, patient global assessment; PhGA, physician global assessment; ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score based on C-reactive protein; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; SJC, swollen joint count; TJC, tender joint count; CRP, C-reactive protein; VAS, visual analog scale. Observed data.
Discriminatory ability of categorical clinical response criteria
Among the response criteria used in both studies, ACR20/50 and PSpARC40/50 performed comparatively well in differentiating between ADA and PBO treatment with c2 (in ABILITY-2 and the TIPES trial respectively) for ACR20 of 16.05 and 11.79; for ACR50, 13.66 and 8.58; for PSpARC40, 8.18 and 8.58; for PSpARC50, 13.46 and 7.13 (Table 3). PSpARC70 showed significant discriminatory ability in ABILITY-2, although not in the TIPES trial (c2 13.49 and 3.26, respectively). Among the AS-specific measures used in ABILITY-2 and the TIPES study respectively, ASDAS-ID (c2 7.17 and 10.13), ASDAS-CII (c2 9.44 and 6.91) and BASDAI50 (c2 10.90 and 7.13) showed significant discriminatory activity across trials. As expected, the TIPES trial reached less discrimination compared to ABILITY-2.
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Table 3. Discrimination between patients on adalimumab versus placebo at week 12 using clinical response criteria
a N=81, b N=80, c N=77, dN=78. χ2, Chi-square; ADA, adalimumab; PBO, placebo; PSpARC, peripheral SpondyloArthritis response criteria; ASDAS-MI, Ankylosing Spondylitis Disease Activity Score-major improvement; ASDAS-CII, ASDAS-clinically important improvement; ASDAS-ID, ASDAS-inactive disease; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; ACR, American College of Rheumatology. Observed data.For TIPES, modified PSpARC and ACR were calculated.
DISCUSSION
In conducting trials, as well as in monitoring patients in clinical practice, there is a need to define the optimal measures for disease activity and clinical response. This is acknowledged as an important research focus for pSpA, given the growing awareness and diagnosis of this disease and the need for new therapies. In our assessment of the performance and hierarchy of outcomes in two independent RCTs, we have found that among the status measures evaluated for disease activity, ASDAS-CRP, BASDAI, PGA, patient global pain and PhGA consistently had both, the highest sensitivity to change from baseline and the highest level of discriminatory ability. Concerning the response criteria (to be used in RCTs), in both trials ACR20 and PSpARC50/70 performed best in terms of discrimination. Previously, a similar analysis in AS18 determined that ASDAS-CRP performed extremely well compared to other outcome measures with respect to sensitivity to change and discrimination.
The two RCTs used different inclusion criteria: ABILITY-2 used the ASAS criteria, whereas TIPES used the ESSG/Amor criteria, resulting in slight differences in the patient populations. Also, the trials partly assessed different outcome measures: PSpARC, ACR and patient global pain were assessed in ABILITY-2 but not TIPES. Therefore, we analyzed them independently. Importantly, this allowed the validation of findings from one population in the other, thus adding robustness. As there is no gold standard for low disease activity and high disease activity in pSpA, we artificially constructed states of low disease activity or
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high disease activity based on two external constructs: PhGA and PGA. Regardless of the external construct used, the AS-specific indices ASDAS-CRP and BASDAI showed the best performance in both trials. The relatively better performance of the ASDAS and BASDAI indices, which were originally developed for AS, may be because both measures include aspects of peripheral joints (the presence of peripheral swelling; BASDAI also includes a question regarding enthesitis).
Interestingly, PGA and PhGA, which are non-disease specific measures, performed as well as ASDAS-CRP and BASDAI (axSpA-specific measures). This finding was consistent across all analyses, supported by the fact that these four outcome measures showed the best discrimination between treatment groups. Notably, these non-disease specific measures were used in the first trials with TNFi in SpA,19, 20 when disease-specific outcome measures had not yet been developed. Possibly a similar cycle of outcome measure development may be required for pSpA. Our data strongly suggest that the perceptions of patients as well as physicians about disease activity are thus far not captured by existing disease activity indices and that the use of axSpA-specific disease measures inherently lacks face validity. The sensitivity and discriminatory ability of almost all these measures was increased in subgroups of patients with higher disease activity at baseline in the ABILITY-2 trial.
Among the response criteria evaluated, the PSpARC and the ACR criteria performed relatively well in both trials. The performance of the ACR20/50, which are used in RA and PsA, in the pSpA population, may be attributed to the overlapping arthritic symptoms between RA and pSpA. Although the ACR response criteria appeared to perform better than the PSpARC, unlike the PSpARC, these do not capture all manifestations of pSpA symptoms, which may limit their usefulness for patients with pSpA. In addition, the TIPES trial did not collect data on patient global pain, enthesitis and dactylitis and therefore the PSpARC was calculated using the PGA, patient global pain (calculated as mean of BASDAI questions 3 and 4), SJC and TJC. The performance of the axSpA-specific response criteria, ASDAS-MI and ASDAS–CII, and BASDAI50, was worse than ACR20 and PSpARC50/70. This is most likely because the cut-off levels for ASDAS-MI/CII and BASDAI50 were obtained and tested in populations with axSpA, and not in populations with pSpA. Our analyses suggest that certain disease activity states are specific to the population in which they have been validated. In other words, it is questionable if ASDAS/BASDAI response criteria should be used in populations with pSpA, despite their very acceptable psychometric characteristics in this regard.
To our knowledge, this is the first study specifically looking into outcome measures in pSpA. A limitation of this study is that due to the different outcomes assessed in the trials, patient global pain, pSpARC40/50/70, and ACR20/50/70 were retroactively derived for TIPES. The differences in performance of some measures between the two studies may have been influenced by smaller sample size of the TIPES trial. The strengths of this study include the reasonably high number of patients, the controlled prospective design, the availability of a
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placebo group for comparison, and the inclusion of many existing outcome measures and response criteria.
In conclusion, the continuous composite outcome measures ASDAS-CRP and BASDAI, as well as the single-item measures, PGA and PhGA, performed consistently well in both pSpA trials, and better than other single-item measures such as CRP and TJC, in detecting change from baseline, and in discriminating between active and placebo treatment. To fully capture typical pSpA manifestations such as enthesitis and dactylitis, it may be worthwhile to develop new composite measures, specific for pSpA, as the performance of PGA and PhGA in this analysis suggests that important parts of the patient’s and physician’s perceptions of disease activity are not yet captured by the current constructs. Regarding the response criteria, our results suggest the use of the disease-specific PSpARC and non-specific ACR criteria in future clinical trials because they represent multiple facets of pSpA disease (face validity), include patient’s and physician’s assessments (face validity), and performed well in both RCTs (discrimination) in comparison to other response criteria evaluated.
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8. Paramarta JE, De Rycke L, Heijda TF, et al. Efficacy and safety of adalimumab for the treatment of peripheral arthritis in SpondyloArthritis patients without ankylosing spondylitis or psoriatic arthritis. Ann Rheum Dis 2013;72(11):1793-9.
9. Mease P, Sieper J, van den Bosch F, et al. Randomized controlled trial of adalimumab in patients with non-psoriatic peripheral spondyloarthritis. Arthritis Rheum 2015;67(4):914-23.
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12. Dougados M, van der Linden S, Juhlin R, et al. The European Spondylarthropathy Study Group preliminary criteria for the classification of spondylarthropathy. Arthritis Rheum
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the classification of spondylarthropathies]. Rev Rhum Mal Osteoartic 1990;57(2):85-9.
14. Lukas C, Landewe R, Sieper J, et al. Development of an ASAS-endorsed disease activity score (ASDAS) in patients with ankylosing spondylitis. Ann Rheum Dis 2009;68(1):18-24.
15. Machado P, Landewe R, Lie E, et al. Ankylosing Spondylitis Disease Activity Score (ASDAS): defining cut-off values for disease activity states and improvement scores. Ann Rheum Dis 2011;70(1):47-53.
16. Braun J, Pham T, Sieper J, et al. International ASAS consensus statement for the use of anti-tumour necrosis factor agents in patients with ankylosing spondylitis. Ann Rheum Dis 2003;62(9):817-24.
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Supplemental Table S1. Baseline characteristics of the study populations in ABILITY-2 and TIPES – ITT
ABILITY-2 TIPESCharacteristics ADA (N=84) PBO(N=81) ADA (N=20) PBO (N=20)
All values are the mean (SD), unless otherwise specified. †2 patients missing. ‡5mg/l is upper limit of normal in both trials. #, number; ITT, Intention to treat; ADA, adalimumab; PBO, placebo; HLA-B27, human leukocyte antigen B27; IBD, Inflammatory Bowel Disease; PGA, patient global assessment; PhGA, physician global assessment; VAS, visual analogue scale; ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score based on C-reactive protein; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; SJC, swollen joint count; TJC, tender joint count; CRP, C-reactive protein; NSAID, nonsteroidal anti-inflammatory drug; DMARD, disease modifying antirheumatic drug; MTX, methotrexate; SSZ, sulfasalazine. aSJC 0-76 joints, bSJC 0-66 joints, cTJC 0-78 joints, dTJC 0-68 joints. For TIPES, patient global pain was derived from the mean of BASDAI #3 and #4.
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Calprotectin serum level is an independent
marker for radiographic spinal progression in
axial spondyloarthritis
Maureen C. Turina1, Joachim Sieper2, Nataliya Yeremenko1,3, Kristina Conrad2, Hildrun Haibel2, Martin Rudwaleit4,
Dominique Baeten1,3, Denis Poddubnyy2
1Department of Clinical Immunology and Rheumatology, Academic Medical Center/
University of Amsterdam, Amsterdam, the Netherlands; 2Rheumatology, Med. Department I, Campus Benjamin Franklin, Charité
Universitätsmedizin Berlin, Berlin, Germany;3Laboratory of Experimental Immunology, Academic Medical Center/University of
Amsterdam, Amsterdam, the Netherlands; 4Endokrinologikum Berlin, Berlin, Germany
Ann Rheum Dis. 2014;73(9):1746–8.
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In previous works, we demonstrated that markers of systemic inflammation (elevated C-reactive protein [CRP] and erythrocyte sedimentation rate [ESR]) are independently associated with radiographic spinal progression over two years in axial spondyloarthritis (axSpA) in the German spondyloarthritis inception cohort (GESPIC).1 We also found previously that calprotectin, which is secreted during monocyte infiltration into inflamed tissues, and thus, directly reflects a potentially important pathophysiological mechanism in SpA,2,3 and which was found to be associated with structural joint damage in psoriatic arthritis4 and in rheumatoid arthritis,5 is clearly elevated in SpA as compared to healthy controls, and decreases rapidly and consistently upon effective treatment,2 although in another work, no differences in serum calprotectin between ankylosing spondylitis patients and healthy controls could be found.6 We aimed here to assess whether serum calprotectin levels are predictive for progression of structural damage in the spine in axSpA.
Seventy-six patients (mean age 38.0±11.5 years, mean symptom duration 4.6±2.8 years, 66% males, 82% HLA-B27-positives) with definite axSpA (n=63 fulfilling the modified New York criteria for ankylosing spondylitis and n=13 patients with axSpA not fulfilling the radiographic part of the modified New York criteria, but with at least one syndesmophyte in the cervical or lumbar spine) from GESPIC,1,7 were selected for this analysis. Detailed description of the cohort and radiographs scoring has been reported elsewhere.1,7-9 Radiographic spinal progression was defined as (1) worsening of the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) by ≥2 units, and (2) development of a new syndesmophyte or progression of existing syndesmophytes (formation of a bridging syndesmophyte) after 2 years. Levels of serum calprotectin were determined by ELISA (Hycult Biotech, the Netherlands).
Baseline calprotectin serum level was significantly higher in patients with mSASSS worsening (n=15) versus those without mSASSS worsening (n=61): mean±SD 0.68±0.21, median 0.69 μg/mL versus mean±SD 0.48±0.26, median 0.42 μg/mL, respectively, p=0.005 (Figure 1A); as well as in patients with syndesmophyte formation/progression (n=18, 12 of them fulfilled also the mSASSS worsening criterion) versus those without (n=58): mean±SD 0.64±0.27, median: 0.65 μg/mL versus mean±SD 0.48±0.25, median 0.42 μg/mL, respectively, p=0.035 (Figure 1B).
A receiver operating characteristic (ROC)-analysis showed a good performance of calprotectin in prediction of mSASSS worsening (area under the curve [AUC]=0.740 (95% CI 0.614 to 0.866), p=0.004; Figure 2A), as well as in prediction of syndesmophyte formation/progression (AUC=0.670 (95% CI 0.520 to 0.819), p=0.031; Figure 2B). In patients with axSpA who already had syndesmophytes at baseline (n=49; 65%), calprotectin demonstrated similar performance, compared to the whole group, as a predictor of radiographic spinal progression: AUC=0.741 (95% CI 0.597 to 0.884), p=0.009 for mSASSS worsening and AUC=0.706 (95% CI 0.547 to 0.866), p=0.020 for syndesmophyte formation/progression.
Calprotectin serum level >0.5 μg/mL (the optimal predictive cut-off in the ROC-analysis) had
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Figure 1. Calprotectin serum levels in patients with and without radiographic spinal progression defined as an mSASSS worsening by ≥2 points over 2 years (A) and syndesmophyte formation/progression (B). Each box indicates the median value, the 1st and the 3rd quartiles; whiskers demonstrate minimal and maximal values, circles – outliers, crosses inside the boxes – mean values. P-values refer to the independent samples t-test. mSASSS, modified Stoke Ankylosing Spondylitis Spine Score.
Figure 2. Receiver Operating Characteristic (ROC) analysis of the association between baseline serum level of calprotectin and radiographic spinal progression defined as an mSASSS worsening by ≥2 points over 2 years (A) and syndesmophyte formation/progression (B) in patients with axial SpA (n=76).
110 CALPROTECTIN FOR RADIOGRAPHIC SPINAL PROGRESSION
a sensitivity of 80%, a specificity of 62%, and an OR=6.2 (95% CI 1.6 to 24.2), p=0.009, as a predictor of mSASSS worsening. As a predictor of syndesmophyte formation/progression, calprotectin serum level >0.5 μg/mL had a sensitivity of 72%, a specificity of 60%, and an OR=4.0 (95% CI 1.2 to 12.6), p=0.020.
Although calprotectin serum level demonstrated a positive correlation with acute-phase reactants (CRP: Spearman’s r=0.382, p=0.001, ESR: r=0.401, p<0.001) and showed an overall performance similar to CRP in prediction of radiographic progression, the association of high calprotectin with radiographic spinal progression remained significant after adjustment for CRP and other risk factors (syndesmophytes at baseline and smoking): OR=5.5 (95% CI 1.2 to 25.8), p=0.030, for mSASSS worsening and an OR=4.1 (95% CI 1.2 to 32.0), p=0.028 for syndesmophyte formation/progression.
Also, calprotectin demonstrated a significant correlation with vascular endothelial growth factor (VEGF) – another biomarker with predictive value for radiographic spinal progression in axSpA:9 Spearman’s r=0.552, p<0.001. After adjustment for VEGF, calprotectin remained significantly associated with mSASSS worsening (OR=4.7 [95% CI 1.1 to 20.5], p=0.040) while the association with syndesmophyte formation has lost statistical significance (OR=3.6 [95% CI 1.0 to 13.7], p=0.056).
Thus, calprotectin represents a novel predictive biomarker for radiographic spinal progression in axial SpA.
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REFERENCES
1. Poddubnyy D, Haibel H, Listing J, et al. Baseline radiographic damage, elevated acute-phase reactant levels, and cigarette smoking status predict spinal radiographic progression in early axial spondylarthritis. Arthritis Rheum 2012;64:1388-98.
2. De Rycke L, Baeten D, Foell D, et al. Differential expression and response to anti-TNFalpha treatment of infiltrating versus resident tissue macrophage subsets in autoimmune arthritis. J Pathol 2005;206:17-27.
3. Kruithof E, De Rycke L, Vandooren B, et al. Identification of synovial biomarkers of response to experimental treatment in early-phase clinical trials in spondylarthritis. Arthritis Rheum 2006;54:1795-804.
4. Madland TM, Larsen A, Brun JG. S100 proteins calprotectin and S100A12 are related to radiographic changes rather than disease activity in psoriatic arthritis with low disease activity. J Rheumatol 2007;34:2089-92.
5. Hammer HB, Odegard S, Syversen SW, et al. Calprotectin (a major S100 leucocyte protein) predicts 10-year radiographic progression in patients with rheumatoid arthritis. Ann Rheum Dis 2010;69:150-4.
6. Klingberg E, Carlsten H, Hilme E, et al. Calprotectin in ankylosing spondylitis--frequently elevated in feces, but normal in serum. Scand J Gastroenterol 2012;47:435-44.
7. Rudwaleit M, Haibel H, Baraliakos X, et al. The early disease stage in axial spondylarthritis: Results from the german spondyloarthritis inception cohort. Arthritis Rheum 2009;60:717-27.
8. Poddubnyy D, Rudwaleit M, Haibel H, et al. Effect of non-steroidal anti-inflammatory drugs on radiographic spinal progression in patients with axial spondyloarthritis: results from the German Spondyloarthritis Inception Cohort. Ann Rheum Dis 2012;71:1616-22.
9. Poddubnyy D, Conrad K, Haibel H, et al. Elevated serum level of the vascular endothelial growth factor predicts radiographic spinal progression in patients with axial spondyloarthritis. Ann Rheum Dis 2013 [Epub ahead of print].
General discussion and summary 8
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GENERAL DISCUSSION AND SUMMARY
Spondyloarthritis (SpA) is an inflammatory disease of the axial skeleton and peripheral joints which can be associated with extra-articular manifestations such as uveitis, psoriasis and inflammatory bowel disease (IBD). In this thesis we have addressed four key questions:
1) Can we find tools for early diagnosis? Currently, the delay between first symptoms and diagnosis is still 5-10 years. As non-steroidal anti-inflammatory drugs (NSAIDs) and anti-tumor necrosis factor (TNF) treatment are also effective in early disease, reducing this diagnostic and therapeutic delay could lead to major gains in overall health, function, and quality of life;
2) Can we use serum biomarkers to predict treatment response? Since a number of new treatments are available to treat SpA effectively, it is important to predict which patients will respond optimally to which treatment;
3) Can we identify outcome measures for peripheral SpA? We have well validated outcome measures in axial SpA which allow us to reliably determine the effectiveness of therapeutic interventions; this is currently lacking in peripheral SpA;
4) Can we find markers that predict structural damage? Structural damage in SpA is often characterized by new bone formation rather than by bone destruction (such as in RA). Although we can halt joint destruction with TNF blockade, we are currently not able to significantly modulate new bone formation.
This thesis contributes to addressing these challenges by exploring the value of serum biomarkers, either as single tools or in the context of composite outcome measures.
EARLY DIAGNOSIS
Current strategies
The diagnostic delay of axial SpA is still approximately 5-10 years.1–3 Of note, data on the delay between first symptoms and diagnosis in peripheral SpA are still lacking. Diagnosing SpA in the early phase of the disease has become increasingly important, since 1) disease activity as measured by signs and symptoms of inflammation is similarly high in early and established disease,4,5 2) treatments used to treat signs and symptoms in established disease are equally effective in early disease,6–11 and 3) patients may respond better to treatment in the early phase of the disease.12 In the past decade, a number of strategies have been developed to capture the disease in the early phase.
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The first is the development of early referral procedures from the general practitioner or orthopedic surgeons to the rheumatologists. Several referral criteria have been evaluated, using back pain, inflammatory back pain (IBP), human leukocyte antigen-B27 (HLA-B27) positivity, sacroiliitis on magnetic resonance imaging (MRI), positive family history, and good response to NSAIDs as most important criteria.13–17 Overall, the less complex strategies appeared to be most efficiently leading to the diagnosis of axial SpA by the rheumatologist in 16-45% of the referred patients.13–15,18 Still, the diagnostic delay remained above five years, indicating that there is still need for additional tools for the early detection and diagnosis of SpA.
The second strategy to capture axial SpA in the early phase is the use of MRI. In contrast to classical radiographic imaging, MRI can detect axial inflammation before the appearance of structural changes such as erosions and new bone formation. Although this is a very interesting topic to discuss, it is beyond the scope of this thesis.
To conclude, the combination of early referral strategies and the use of MRIs of the SI joints already decreased significantly the diagnostic delay of axial SpA, but the delay on average still remains more than 5 years. The search for other strategies and tools to detect and identify the disease in (very) early phase thus remains important.
Peripheral blood biomarkers
One potential way to decrease the diagnostic delay is the use of biomarkers. A biomarker is defined as a “characteristic that can be objectively measured and evaluated as an indicator of a normal biologic process, a pathophysiologic process, or a pharmacologic response to a therapeutic intervention”.23 Biomarkers can be derived of any tissue or body fluid. Focusing on one of the target tissues of SpA, the peripheral synovitis, our group has previously reported clear histological, cellular, and molecular differences between SpA and other rheumatic conditions.24–27 Although some of these features may also have a diagnostic value, sampling target tissues is a relatively complex and invasive procedure which cannot easily be used in daily clinical settings. Obviously, peripheral blood would be a much more convenient and reliable source for diagnostic biomarkers. Several peripheral blood-derived biomarkers have already been evaluated for diagnostic properties in SpA:
1) Genetic risk factors: the major genetic risk factor for ankylosing spondylitis (AS), the prototype of axial SpA, is HLA-B27. Although 80-90% of the AS patients carry the HLA-B27 gene (and 40-60% in other subtypes),28 HLA-B27 is also found in up to 8% of the general Western population. Accordingly, the positive predictive value of HLA-B27 is rather limited in the absence of a clear clinical suspicion.29,30 As discussed for MRI, testing for HLA-B27 positivity is also only meaningful in individuals with sufficient clinical suspicion of SpA.
2) Several serum markers, including C-reactive protein (CRP), erythrocyte sedimentation
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rate (ESR), and calprotectin, were shown to be elevated in full-blown active SpA compared to healthy controls, and to decrease upon effective treatment.31–33 In chapter 3, however, we demonstrated that these serum inflammatory biomarkers were not or, in case of calprotectin, only marginally elevated in the SPACE cohort (n=310) when comparing early axial SpA with ‘control’ early back pain patients, and that therefore these markers are not useful as early diagnostic markers. To screen for other new candidate biomarkers, we first performed a literature search in chapter 2 on informative biomarkers in related immune-mediated inflammatory diseases, namely psoriasis and IBD. We concluded that human beta defensin-2 (hBD-2)34–37 and lipocalin-2,38–44 were the most interesting candidates to test in SpA since these are interleukin (IL)-17 driven markers and since the IL-23/IL-17 is a major pathogenic cytokine pathway in SpA. Second, we identified IL-27, a cytokine belonging to the IL-23/IL-12 family, as an additional candidate maker since one recent report showed elevated serum levels in full-blown AS versus healthy controls.45 In chapter 3 we determined the serum levels of these three markers in AS and healthy controls but did not detect differences between the two groups. Therefore we did not test these markers in the SPACE cohort. We concluded that the aforementioned serum inflammatory biomarkers were not useful for diagnosing axial SpA at the early phase of the disease.
Two important aspects should be considered when interpreting these data. First, as we did not perform a systematic ‘omics’ approach to find diagnostic serum biomarkers but rather used a targeted approach based on literature data, it cannot be excluded that we have missed interesting, yet unknown serum diagnostic biomarkers. Second, our findings are in line with the concept that SpA is a tissue-specific disease rather than a systemic inflammatory disease and that therefore measuring markers in peripheral blood is not informative. This concept is further supported by our unpublished observations that a) disease-specific molecular and cellular signatures found in target tissues (e.g. myogene signature in SpA synovitis),27 cannot be detected in peripheral blood, and b) global transcriptomic analyses by pan-genomic microarray on peripheral blood cells of early SpA patients versus ‘control’ back pain patients from the SPACE cohort failed to reveal disease-specific expression signatures (Yeremenko and Turina, unpublished data).
3) Auto-antibodies: in contrast to many other rheumatic diseases, SpA is not characterized by the presence of disease-specific autoantibodies.46 Several approaches have been used to screen for potential autoantibodies but overall the results have been disappointing. Duftner et al.47 showed that serum concentrations of antibodies binding to the procaryotically expressed 28-kDa protein were higher in AS versus healthy controls. Chou et al.48 found that levels of anti-agalactosyl immunoglobulin-G antibody (anti-Gal(0) IgG) were elevated in AS and psoriatic arthritis when compared with healthy controls. In another study, plasma of AS, rheumatoid arthritis, and healthy controls, were screened for 3498 proteins, using two protein arrays to determine autoantibodies. In total, 44%, 33% and 8% of the individuals in the different groups had a broad autoantibody response, respectively.49 Nevertheless, all the
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aforementioned results had low sensitivities and specificities, and were never reproduced in independent cohorts. Therefore these autoantibodies do not appear to be useful for diagnostic purposes.
Recently, one group demonstrated IgG-antibodies against CD74 specific for HLA class II-associated invariant chain peptide (CLIP) with high sensitivity (85.1%) and specificity (92.2%) for SpA.50,51 We are currently in the process of confirming these data in our cohorts. In contrast to the published data, and despite using the same assay in the same laboratory, IgG-antibodies against CD74 levels neither were elevated in full-blown AS versus healthy controls nor in early axial SpA versus early ‘control’ back pain patients. Nevertheless, ongoing analyses suggest that anti-CD74 IgA antibodies may be elevated in active AS versus healthy controls with a sensitivity of 38% and a specificity of 95%. In the near future, we will determine anti-CD74 IgA in the SPACE cohort to see whether these autoantibodies may have an early diagnostic value.
Inception cohorts
A key requisite for the search for novel diagnostic biomarkers is the availability of appropriate inception cohorts. An inception cohort is a longitudinal cohort with a predefined group of persons gathered at a specific time point as early as possible in the development of a specific disorder. These cohorts could facilitate the search for valuable clinical, biological, and imaging biomarkers with the ultimate goal to dramatically decrease the time to diagnosis and start treatment without delay. In contrast to longitudinal studies, cross-sectional studies are found to be obsolete for this purpose.52 Several interesting inception cohort studies have been initiated over the last decade. GESPIC5 is an inception cohort of diagnosed AS and nr-axSpA patients with a maximum symptom duration of 10 and 5 years, respectively, which is very useful for the analysis of progression of structural damage. Esperanza53 is a cohort with patients having SpA features for at least 3 months and at most 2 years. DESIR54 and SPACE55 included patients with inflammatory back pain of 3 years at most, or back pain of 2 years at most, respectively. As described in chapter 4, we have initiated a different inception cohort study of seemingly healthy (i.e. individuals who are not known with musculoskeletal complaints by the general practitioner or rheumatologist) first-degree relatives (FDRs) of HLA-B27 positive patients (the so called ‘Pre-SpA’ cohort). The estimated recurrence risk for SpA in these relatives is 12%, which is much higher than the 0.5-1.5% risk in the general population.29,30,56 In contrast to other cohorts, in which clinical signs and symptoms (most often back pain) are required for inclusion, the Pre-SpA cohort thus focuses on baseline evaluation and prospective follow-up of non-symptomatic individuals at risk. In the first pilot analysis of Pre-SpA, we found that 17 out of 51 (33%) FDRs already fulfilled SpA classification criteria (the Assessment of Spondyloarthritis international Society [ASAS] axial SpA and/or the European Spondylarthropathy Study Group [ESSG] criteria)16,57 at baseline. Although fulfilling classification criteria does not necessarily imply the presence
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of a clinical diagnosis, these preliminary data suggest the presence of unrecognized disease in a significant proportion of FDRs. Interestingly, a similar proportion of HLA-B27+ and HLA-B27- FDRs fulfilled the classification criteria. Moreover, 6 of the 38 (16%) FDRs who did not fulfill the classification criteria had imaging abnormalities suggestive of SpA. Further follow-up of these patients will clarify who will develop established SpA, and will shed light on the question if these early abnormalities should be considered false positive. In the future, we will perform several other analyses in these FDRs (e.g. serum markers, genetics) in the search for new biomarkers with the ultimate goal to decrease the diagnostic delay of SpA. Based on the preliminary data from this pilot study, we are now coordinating a national study in 6 SpA centers of excellence (AMC, VUMC, LUMC, MUMC, UMCG, and Maasstad hospital) aimed to include and prospectively monitor 500 FDRs.
To conclude, diagnosing axial SpA at the early phase of the disease (at an earlier phase than currently possible) is an important but difficult goal. Early referral strategies and MRIs have resulted in a significant decrease of the diagnostic delay, but the delay should be further diminished. Investigations of serum biomarkers have not yet resulted in reliable diagnostic tools. Potential leads are the anti-CD74 IgA antibodies and the use of new ‘omics’ technologies. In all cases, the availability of large and well-documented early and preclinical SpA inception cohorts is essential for the evaluation and validation of diagnostic biomarkers.
PREDICTING TREATMENT RESPONSES
Treatment regimen
Although the number of registered treatment for SpA is still limited when compared with rheumatoid arthritis, the therapeutic choices are rapidly expanding. In axial SpA, treatment options are limited to NSAIDs58 and TNF inhibitors.6,11,59,60 In peripheral SpA, patients can be treated with local steroids, disease-modifying antirheumatic drugs (DMARDs) such as sulfasalazine,61,62 and TNF inhibitors.9,10 In psoriatic arthritis, patients can be treated additionally with DMARDs such as leflunomide,63–65 apremilast66,67 and methotrexate,68,69 although the effectiveness of the latter DMARD is subject to debate despite common use in clinical practice. Ustekinumab (a monoclonal antibody against the p40 subunit of IL-23 and IL-12),70–72 is a non-TNF inhibitor biological recently registered for psoriatic arthritis. An overview of the currently available therapies is given in Table 1.
Besides the currently available drugs, an exciting new therapeutic option in both AS and psoriatic arthritis is blockade of IL-17, either by using monoclonal antibodies directed against IL-17A (such as secukinumab and ixekizumab) or by monoclonal antibodies blocking IL-17 receptors (such as brodalumab). Large phase III studies showed that secukinumab is effective and safe in both AS and psoriatic arthritis, and this drug is currently in the
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Table 1. An overview of currently available treatment options in ankylosing spondylitis and psoriatic arthritis
registration phase.70,76,77 Many other drugs, including biologics as well as small molecules, are currently in phase II or III clinical trials in AS and/or psoriatic arthritis (Table 2), with many more in preclinical development. An extensive overview of recent and ongoing clinical trials in SpA was recently provided by Paramarta et al.78
The increasing number of treatment options urge an appropriate prediction, preferably prior to the start of therapy, about which patients will respond well to which treatments in the long-term. For example, 20-40% of the patients do not respond well to TNF inhibitors.56 In clinical practice, a significant part of these partial responders are continuing on TNF inhibitors since there are no other treatment options. With the advent of IL-17 blockade and hopefully other compounds in the near future, it becomes increasingly important to select an adequate strategy prior to the start of the treatment.
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Table 2. An overview of ongoing clinical trials in ankylosing spondylitis and psoriatic arthritis
Drug group Clinical trial phase Mode of action SpA subtype Trial name and reference
Small moleculesTofacitinib Phase 2/Phase 3
JAK inhibitor PsA OPAL
Thalidomide Phase 2 TNF and IL-12 Inhibitor AS NAApremilast Phase 3
Several studies have focused on the identification of baseline predictors for treatment response in clinical trials at the group level in axial SpA. Of note, data on baseline predictors in peripheral SpA are lacking. Identifying such baseline predictors is important for designing new clinical studies, in which stratification at baseline is based on these predictors. A post-hoc analysis82 of two clinical trials with active AS patients (n=99) receiving infliximab versus placebo, or etanercept versus placebo and showed that age, Bath ankylosing spondylitis functional index (BASFI), disease duration, and elevated CRP/ESR levels were good predictors for treatment response at week 12, defined by Bath akylosing spondylitis disease activity index (BASDAI). Recently, another large pooled analysis was performed on four randomized controlled trials with etanercept versus sulfasalazine or placebo in 1281 active AS patients to determine the predictors for clinical remission as expressed by ASAS partial remission.83 In this analysis short disease duration of ≤ 2 years and age ≤ 40 years at the time of diagnosis, were good baseline predictors for clinical remission at week 12. Regarding biomarkers in this analysis, patients with elevated CRP levels showed better responses to treatment when compared with patients with normal baseline CRP levels. Similar results were found in other clinical trials with TNF inhibitors83–85 as well as in large observational cohorts with AS patients receiving TNF inhibitors.86,87 To summarize, the baseline predictors short disease
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duration, young age at time of diagnosis, high BASFI scores, and elevated CRP/ESR levels are associated with good response to treatment at week 12. For the scope of this thesis, we have focused exclusively on the biomarkers.
Many recent clinical trials, and mainly those conducted in the early and non-radiographic forms of axSpA (nr-axSpA), have elevated CRP levels or a positive MRI of the sacroiliac (SI)-joints as an important eligibility criterion at screening and/or baseline, which seems justified based on the aforementioned results. Nevertheless, a sub-analysis of ABILITY-1,10 a phase 3 randomized controlled trial with nr-axSpA patients receiving adalimumab or placebo, showed that CRP is indeed a good predictor for clinical response at week 12, but not for response at year 1 and year 3. This finding suggests that CRP does reflect clinical response at the short term but does not reflect a ‘true responder’ who still responds well to adalimumab treatment at the long term. Moreover, CRP is a non-stable biomarker that can easily fluctuate between elevated and normal CRP levels over time, especially around the ‘upper limit of normal’ levels. For example, in the placebo arm of the same ABILITY-1 trial, 14 out of 57 (25%) patients with normal CRP levels at baseline converted into ‘elevated CRP’ between baseline and week 12.88 We recently confirmed the latter result in nr-axSpA patients and AS patients, using the placebo arm of RAPID-axSpA, a phase-3 double-blind randomized controlled trial with certolizumab pegol (MSD) or placebo for 16 weeks.11 Thirteen of the 26 (50%) patients with normal CRP levels at baseline, had elevated levels of CRP in 1-6 consequent visits in the placebo arm (Turina et al., unpublished data). The results of these two analyses suggest that clinical trials should not use single measurements of CRP as a major eligibility criterion. Whether this is also true for MRI, is beyond the scope of this thesis.
The prediction of treatment response is not only important for stratification in clinical trials and for clinical research, but also for the decision-making process of the rheumatologist in individual patients in clinical practice. In AS for example, the clinical decision to start TNF inhibitors is based on a strategy that proclaims TNF inhibitor treatment could be started when a patient has consistently active disease, as expressed by BASDAI≥4, despite the optimal use of NSAIDs.89,90 Since the available effective treatments are expensive and come along with numerous side-effects, ideally the rheumatologist should be able to estimate in advance that a certain patient will have beneficial effects from the treatment. All the aforementioned parameters (including elevated CRP) are informative predictors at the group level, but fail to predict at the individual level.91–93 Thus, we need not only more reliable and robust markers of response to treatment but also markers with sufficient sensitivity and specificity to have a high predictive value in individual patients.
Measuring early changes after treatment
Since at the individual patient level biomarkers at baseline cannot predict whether patients will respond to a certain treatment, an interesting alternative concept might be to search for
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early changes of biomarker levels between baseline and shortly after the start of treatment (e.g. baseline and 2 weeks after treatment). One would expect significant decreases in certain biomarker levels over a short period of time when effective treatment is started. This theory is based on the finding that ‘true’ responders will respond early to treatment, as was published in a post-hoc analysis from the phase 3 ATLAS randomized controlled trial.94 Two hundred-two active AS patients of the total 311 (65%) participating patients received at least one dose of adalimumab and completed five years of follow-up. The best predictor for remission (as expressed by ASAS partial remission and Ankylosing Spondylitis Diseases Activity Score [ASDAS]-inactive disease at year 1 and year 5) was the achieved remission (by ASAS partial remission or ASDAS-inactive disease) after 12 weeks of treatment. Similar results were seen in the post-hoc analysis in peripheral SpA in the ABILITY-2 study, a phase 3 randomized controlled trial where patients received adalimumab or placebo at the first 12 weeks (double blind period) prior to the open label phase up to three years.95 ASDAS-inactive disease or Peripheral SpA Response Criteria (PSpARC) remission at week 12 were the best predictors for clinical remission (ASDAS-inactive disease or PSpARC remission) at years 1 and/or 3, when compared to baseline characteristics. The results of the two studies indicate that a ‘true’ responder to TNF inhibitors in the long term can be predicted by reaching an early response (short term outcome, i.e. 12 weeks of treatment) to this treatment rather than by baseline features alone.
An interesting approach to predict treatment responses very shortly after the start of treatment was demonstrated in chapter 5. Here we evaluated early changes in serum biomarker levels after TNF blockade was initiated. Serum was collected from axial and peripheral SpA patients of a randomized controlled trial, and two open label trials with TNF inhibitors. The latter two cohorts were considered as validation cohorts. These were all proof-of-concept trials, indicating that the sample sizes were relatively small. We selected seven serum biomarkers (hs-CRP, interleukin-6, pentraxin-3, alpha-2-macroglobulin, matrix metalloproteinase-3 [MMP-3], calprotectin, and vascular endothelial growth factor [VEGF]) and determined the levels at baseline and after two or four weeks of treatment, depending on the cohort design. We aimed to determine which of the biomarkers had a high sensitivity to rapid change upon effective treatment in SpA in proof-of-concept trials. We found that in all three cohorts, calprotectin and hs-CRP were good markers with high sensitivity to change upon effective treatment in both axial and peripheral SpA, whereas the levels did not decrease in the placebo arm. We did not find similar results for the other five biomarkers. Although this finding was only based on TNF inhibitors, early changes of calprotectin and CRP levels were also detected in our proof-of-concept trial with secukinumab,76 thereby implying that early changes of calprotectin and CRP levels after effective treatment are not restricted to a certain mode of action. Although these results are only applicable at the group level in a proof-of-concept setting, the detection of early changes of biomarker levels is an interesting approach to further study at the individual level. Once this approach is applicable in clinical practice, the rheumatologist could decide on the treatment regimen
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within two weeks, i.e. maintain the treatment or switch between TNF and IL-17 inhibitors in SpA.
IDENTIFYING OUTCOME MEASURES IN SPA
Objective markers for inflammation versus patient-reported outcomes
Biomarkers may not only be useful for early diagnosis and prediction of treatment responses but also for monitoring disease activity in trials, clinical research as well as clinical practice. Historically, the BASDAI and the Visual Analogue Scales (VAS) for pain or patient global assessment of disease activity have been well validated and broadly used. These measures, however, have two major drawbacks.
First, as most outcome measures used in clinical research in the field of SpA, the BASDAI (a composite score of questions on tiredness, back pain, peripheral pain, enthesitis and morning stiffness) and VAS measures rely completely on patient-reported outcomes (PROs) and therefore may be influenced by many other factors (e.g. intercurrent pathologies, psycho-social factors) besides genuine ‘biological disease activity’. The major issue here is that we still lack biomarkers that directly reflect disease activity in SpA, with CRP levels probably being currently the best ‘proxy’. Therefore, combination of PROs and objective measures such as CRP in a composite index might be the most informative manner to determine disease activity in SpA at the moment. One disease activity index that includes both PROs and an objective measure, is the Ankylosing Spondylitis Disease Activity Score (ASDAS).96,97 ASDAS is a composite of CRP levels and of questions on back pain, patient global, peripheral pain/swelling, and morning stiffness. The discriminatory ability of ASDAS is higher than that of BASDAI, a purely PRO driven composite index.96,98
Second, most disease activity measures have only been validated and used in axial disease, and it remains unknown if they also adequately reflect peripheral disease manifestations. Several other tools have been used to measure peripheral arthritis, enthesitis, and dactylitis in psoriatic arthritis, but these outcome measures then do not capture axial disease activity. As a large proportion of SpA patients display both axial and peripheral disease, we assessed in chapter 6 if composite disease activity indices used in axial SpA could also be used to assess peripheral SpA. Comparing several continuous outcome measures in two independent randomized controlled trials with adalimumab versus placebo in peripheral SpA, we showed that ASDAS and BASDAI performed equally well in terms of sensitivity to change and in discriminatory ability in peripheral disease. Since ASDAS does perform better than BASDAI in axial SpA, we recommend the use of ASDAS (which includes CRP) as preferred outcome measure in SpA.
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PREDICTING STRUCTURAL DAMAGE
In SpA, structural damage is characterized by bone and cartilage destruction as well as by new bone formation, which can eventually lead to total fusion (ankylosis) of the axial skeleton (the spine) and peripheral joints. Total fusion of the spine occurs in 28% and 43% of AS patients with a disease duration of 30-40 years and above 40 years, respectively.99 Accordingly, the structural damage due to new bone formation is an important co-determinant (together with active inflammation) of spinal mobility, function, and quality of life over time.100 Whereas TNF blockers can potently inhibit inflammation and joint destruction in SpA, they unfortunately fail to significantly halt new bone formation. Therefore, an ultimate challenge is to halt or even prevent radiographic spinal progression. We will discuss here the different theories on new bone formation in SpA as well as potential strategies to predict which patients will suffer most from this aspect of the disease. Such prediction is very important for a number of reasons. First, it allows to reassure those patients who will not develop pronounced osteoproliferation. Second, it is needed to stratify patients in clinical research on structural damage in SpA. And third, it will be an essential determinant of individualized treatment if future research demonstrates that either very early treatment or drugs targeting different pathogenetic mechanisms (such as potentially the previously discussed IL-17 inhibitors) do halt new bone formation.
Inflammation and new bone formation
There are three main theories about pathophysiological new bone formation. First, Sieper et al.101 hypothesized that remodeling is a repair process triggered by an initial phase of inflammation and tissue destruction. In case this theory is correct, TNF blockade might be able to halt new bone formation only when started in a very early disease stage, again emphasizing the importance of decreasing the diagnostic delay. The key question would then become which patients benefit most from such an early and aggressive treatment approach. Second, Lories et al.102 hypothesized that “entheseal stress” leads to triggering of two largely independent processes: an acute inflammatory reaction, which evolves then to chronic inflammation, and activation of progenitor cells that generate new bone. The uncoupling of inflammation and new bone formation in this model implies that, whereas all patients may require anti-inflammatory therapy, a specific treatment to target the bone remodelling pathway should be developed and given to patients prone to develop spinal new bone formation. Third, based on data in pre-clinical models, our group proposed that new bone formation is directly driven by inflammatory mediators distinct from soluble TNF, including transmembrane TNF (van Duivenvoorde et al., unpublished data) and IL-17A (van Tok et al., unpublished data). If this concept can be translated to human SpA, it would imply that it is crucial to identify which patient will not show extensive new bone formation and may thus be effectively treated with NSAID or TNF inhibitor versus those who may benefit
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from other targeted treatments such as IL-17 blockade.
Current strategies in predicting new bone formation
The “Outcome in AS International Study” (OASIS) cohort, a longitudinal study of 217 consecutive AS patients with a follow-up period of 12 years with clinical and imaging data, allowed to identify a series of clinical and imaging risk factors for radiographic progression of disease. The most important predictors in this study were high disease activity, smoking, HLA-B27 positivity, male gender, older age, and already existing syndesmophytes at baseline.103–105 Also serum biomarkers had been explored in the context of radiological progression of spinal disease, including CRP,106,107 ESR,103 matrix metalloproteinase (MMP-3),108,109 dickkopf-1 (Dkk-1),110–112 visfatin, leptin,113–115 and VEGF.116,117 In chapter 7, we additionally determined the value of calprotectin using the GESPIC cohort. Calprotectin was found to be an independent predictor for new bone formation, but was not superior to CRP. It thus appears that several biomarkers are significantly associated with new bone formation at the group level but, unfortunately, none of these markers is sensitive and specific enough to be used for prediction of structural damage in individual patients. Besides clinical features and biomarkers, multiple studies have explored the value of MRI visualization of inflammation and fatty changes as predictor of new bone formation. As the published results are partially discrepant118,119 and as imaging was not the focus of this thesis, we will not discuss this here in detail. However, it is crucial to realize that novel imaging technologies, including but not restricted to MRI, may form a very promising venue to measure objectively inflammatory and structural tissue changes in SpA and thereby may in the future be more appropriate than serum biomarkers for SpA detection, monitoring, and prediction. To illustrate this concept, we will briefly discuss here novel developments in the use of PET-CT in axial SpA.
PET-CT imaging with specific tracers for the detection of new bone formation
Positron emission tomography-computed tomography (PET/CT) or PET/MRI allows to visualize the uptake of specific radiolabelled tracers in tissues and cells. For example, labelled glucose will be taken up by metabolically active tissues. Our colleagues form the VUMC recently explored the value of PET/CT with [18F]-fluoride as the uptake of this specific tracer in bone represents the blood flow and osteoblastic bone synthesis and activity at a specific location. A pilot study compared [18F]-fluoride PET/CT, MRI and X-ray of the spine in six TNF inhibitor naïve AS patients.120 An increased uptake of [18F]-fluoride on PET/CT was associated with corner inflammatory lesions (CIL) on MRI, and with existing syndesmophytes on the X-ray of the spine (OR=55.1; 95% CI, 7.3-422.3; p<0.001). Buchbender et al.121 studied PET/MRI-SI joint and spine in 13 active, TNF inhibitor naive AS patients according to the mNY criteria. They reported that [18F]-fluoride PET/MRI bone marrow edema and to a lesser extent fatty deposition was associated to osteoblastic activity, whereas structural changes (including
126 GENERAL DISCUSSION AND SUMMARY
sclerosis, erosions, ankylosis) were not frequently associated with osteoblastic activity. This is an interesting finding since the osteoblast activity was seen at sites where no structural changes were seen on MRI. Moreover, at several sites, elevated [18F]-fluoride uptake was seen whereas simultaneous MRI abnormalities were not depicted.
Although these studies are still preliminary and more data from follow-up studies are awaited, both studies illustrated well the potential of new molecular imaging techniques to visualize, measure, and monitor the disease processes in the target tissues of SpA. As our data presented here in this thesis tend to suggest that SpA disease processes are not easily captured by serum biomarkers and as most target tissues of SpA (such as spine, SI joints, and entheses) are difficult to approach, molecular imaging should probably be an area of major research investment in the future years.
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101. Sieper J, Appel H, Braun J, Rudwaleit M. Critical appraisal of assessment of structural damage in ankylosing spondylitis: implications for treatment outcomes. Arthritis Rheum 2008;58(3):649–56.
102. Lories RJU, Luyten FP, de Vlam K. Progress in spondylarthritis. Mechanisms of new bone formation in spondyloarthritis. Arthritis Res Ther 2009;11(2):221.
103. Van Tubergen A, Ramiro S, van der Heijde D, Dougados M, Mielants H, Landewé R. Development of new syndesmophytes and bridges in ankylosing spondylitis
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and their predictors: a longitudinal study. Ann Rheum Dis 2012;71(4):518–23.
104. Ramiro S, van der Heijde D, van Tubergen A, et al. Higher disease activity leads to more structural damage in the spine in ankylosing spondylitis: 12-year longitudinal data from the OASIS cohort. Ann Rheum Dis 2014;73(8):1455–61.
105. Ramiro S, Stolwijk C, van Tubergen A, et al. Evolution of radiographic damage in ankylosing spondylitis: a 12 year prospective follow-up of the OASIS study. Ann Rheum Dis 2015;74(1):52–9.
106. Poddubnyy D, Rudwaleit M, Haibel H, et al. Rates and predictors of radiographic sacroiliitis progression over 2 years in patients with axial spondyloarthritis. Ann Rheum Dis 2011;70(8):1369–74.
107. Pedersen SJ, Sørensen IJ, Lambert RGW, et al. Radiographic progression is associated with resolution of systemic inflammation in patients with axial spondylarthritis treated with tumor necrosis factor α inhibitors. Arthritis Rheum 2011;63(12):3789–800.
108. Yang C, Gu J, Rihl M, et al. Serum levels of matrix metalloproteinase 3 and macrophage colony-stimulating factor 1 correlate with disease activity in ankylosing spondylitis. Arthritis Rheum 2004;51(5):691–9.
109. Arends S, van der Veer E, Groen H, et al. Serum MMP-3 level as a biomarker for monitoring and predicting response to etanercept treatment in ankylosing spondylitis. J Rheumatol 2011;38(8):1644–50.
110. Heiland GR, Appel H, Poddubnyy D, et al. High level of functional dickkopf-1 predicts protection from syndesmophyte formation in patients with ankylosing spondylitis. Ann Rheum Dis 2012;71(4):572–4.
111. Klingberg E, Nurkkala M, Carlsten H, Forsblad-d’Elia H. Biomarkers of bone metabolism in ankylosing spondylitis in relation to osteoproliferation and osteoporosis. J Rheumatol 2014;41(7):1349–56.
112. Korkosz M, Jerzy G, Leszczy P, Pawlak-bu K, Jeka S, Kucharska E. High disease activity in ankylosing spondylitis is associated with increased serum sclerostin level and decreased wingless protein-3a signaling but is not linked with greater structural damage. BMC Musculoskelet Disord 2013;14:99.doi:10.1186/1471-2474-14-99.
113. Syrbe U, Callhoff J, Conrad K, et al. Serum adipokine levels in patients with ankylosing spondylitis and their relationship to clinical parameters and radiographic spinal progression. Arthritis Rheumatol (Hoboken, NJ) 2015;67(3):678–85.
114. Genre F, López-Mejías R, Miranda-Filloy J a, et al. Adipokines, biomarkers of endothelial activation, and metabolic syndrome in patients with ankylosing spondylitis. Biomed Res Int 2014;2014:860651.
115. Kim K-J, Kim J-Y, Park S-J, et al. Serum leptin levels are associated with the presence of syndesmophytes in male patients with ankylosing spondylitis. Clin Rheumatol 2012;31(8):1231–8.
116. Poddubnyy D, Conrad K, Haibel H, et al. Elevated serum level of the vascular endothelial growth factor predicts
radiographic spinal progression in patients with axial spondyloarthritis. Ann Rheum Dis 2014;73(12):2137–43.
117. Baraliakos X, Hermann KG, Xu S, Hsu B, Braun J. VEGF and CRP serum levels lack predictive value for outcomes as assessed by conventional radiographs and magnetic resonance imaging in patients with active ankylosing spondylitis treated with the TNF inhibitor golimumab. Ann Rheum Dis 2014;73(Suppl2):1138-1139.
118. Van der Heijde D, Machado P, Braun J, et al. MRI inflammation at the vertebral unit only marginally predicts new syndesmophyte formation: a multilevel analysis in patients with ankylosing spondylitis. Ann Rheum Dis 2012;71(3):369–73.
119. Maksymowych WP, Chiowchanwisawakit P, Clare T, Pedersen SJ, Østergaard M, Lambert RGW. Inflammatory lesions of the spine on magnetic resonance imaging predict the development of new syndesmophytes in ankylosing spondylitis evidence of a relationship between inflammation and new bone formation. Arthritis Rheum 2009;60(1):93–102.
120. Fischer DR, Pfirrmann CWA, Zubler V, et al. High bone turnover assessed by 18F-fluoride PET / CT in the spine and sacroiliac joints of patients with ankylosing spondylitis: comparison with inflammatory lesions detected by whole body MRI. Ann Rheum Dis 2012;71(Suppl3):606.
121. Buchbender C, Ostendorf B, Ruhlmann V, et al. Hybrid 18F-labeled Fluoride Positron Emission Tomography/Magnetic Resonance (MR) Imaging of the Sacroiliac Joints and the Spine in Patients with Axial Spondyloarthritis: A Pilot Study Exploring the Link of MR Bone Pathologies and Increased Osteoblastic Ac. J Rheumatol First Release July 1 2015; doi:10.3899/jrheum.150250.
APPENDICES
Nederlandse samenvattingDankwoord
PhD portfolioCurriculum vitae
List of publications&
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NEDERLANDSE SAMENVATTING
Spondyloartritis (SpA) is een frequent voorkomende vorm van chronische gewrichtsontsteking die zowel het axiale skelet (sacro-iliacaal gewrichten en de wervelkolom) als de perifere gewrichten (met name oligoartritis [1-5 gewrichten] van de grote gewrichten zoals knieën en enkels) aantast. Axiale SpA kenmerkt zich door ontstekingsachtige rugpijn. Deze rugpijn uit zich door pijn in rust, verbetering bij beweging, nachtelijke pijn en ochtendstijfheid. Het proces van spinale ontsteking verloopt gelijktijdig met pathologische botnieuwvorming, die op zijn beurt kan leiden tot totale verbening van de sacro-iliacaal (SI-)gewrichten en de wervelkolom. Het prototype van axiale SpA is ‘spondylitis ankylopoietica’, ook wel de ziekte van Bechterew genoemd. Perifere SpA symptomen bestaan uit pijnlijke, warme, stijve en gezwollen gewrichten, en uit enthesitis (ontsteking ter hoogte van een peesaanhechting) en/of dactylitis (ontsteking van een gehele vinger [‘worstvinger’] of teen [‘worstteen’]). Bij deze vorm van SpA kan zowel botdestructie als pathologische botnieuwvorming worden gezien. Het prototype van perifere SpA is artritis psoriatica. Daarnaast kunnen extra-articulaire manifestaties voorkomen zoals ontstekingen van de ogen (uveitis anterior), de darmen (inflammatoire darmziekten [IBD]: de ziekte van Crohn en colitis ulcerosa) en van de huid (psoriasis).
De behandeling van SpA in zijn algemeenheid is momenteel nog tamelijk beperkt: patiënten met axiale SpA worden behandeld met ‘non-steroidal antinflammatory drugs’ (NSAIDs) en (bij onvoldoende effect) met tumor necrosis factor (TNF)-alpha-remmers. Patiënten met perifere SpA kunnen worden behandeld met NSAIDs, maar ook met ‘disease-modifying antirheumatic drugs’ (DMARDs) en (bij onvoldoende effect) met TNF-remmers. Bij beide vormen van SpA hebben de huidige behandelingen goed effect op de symptomen en remmen zij bij perifere SpA ook botdestructie. Bij axiale SpA wordt het proces van botnieuwvorming echter niet geremd door de huidige medicatie.
Dit proefschrift
In dit proefschrift trachten wij vier belangrijke vragen te beantwoorden over de diagnose, behandeling en de uitkomst van SpA: 1) diagnose: kunnen we (bio-)markers identificeren die bijdragen aan het diagnosticeren van SpA in de vroege (klinische en subklinische) fase van de ziekte? Het is belangrijk de periode tussen het ontstaan van symptomen en het diagnosticeren (de zogenaamde ‘diagnostic delay’) van axiale SpA, die gemiddeld 5 tot 10 jaar duurt, te verkorten. 2) Respons op behandeling: kunnen we serum biomarkers identificeren voor het voorspellen van respons op nieuwe therapieën in kleinschalige, kortdurende ‘proof-of-concept’ (PoC) klinische trials? 3) Respons op behandeling: kunnen we uitkomstmaten valideren voor het voorspellen van respons op therapie in perifere SpA? Deze vragen zijn van belang vanwege de beperkte therapeutische mogelijkheden bij SpA. 4) Prognose: kunnen we biomarkers identificeren die voorspellend zijn voor de progressie van
136 APPENDICES
structurele schade in de wervelkolom in axiale SpA? De pathologische botnieuwvorming in axiale SpA komt slechts bij een minderheid van de patiënten voor en het lijkt belangrijk deze groep van tevoren te kunnen identificeren. In dit proefschrift brengen wij de klinische en biologische markers in kaart om te trachten deze vragen te beantwoorden.
HET VROEGTIJDIG STELLEN VAN EEN DIAGNOSE SPA
Het vroegtijdig stellen van een diagnose is van belang omdat dan een tijdige behandeling kan worden gestart en omdat bekend is dat de behandeling in een late fase van de ziekte de botnieuwvorming niet remt. Er zijn enkele inflammatoire biomarkers in het serum bekend die mogelijk informatief zijn met betrekking tot SpA, namelijk c-reactief proteïne (CRP), bezinking (BSE) en calprotectine, een heterodimeer bestaande uit S100A8 en A9. In hoofdstuk 3 hebben wij deze drie markers getest in een cohort van patiënten met rugpijn met een duur tussen de 3 maanden en 2 jaar, maar ontstaan is voor het 45e levensjaar (SPondyloarthritis Caught Early [SPACE] cohort). Er werden echter geen belangrijke verschillen aangetoond tussen vroege axiale SpA patiënten (n=119) en ‘controle’ rugpijn patiënten (n=191). Hieruit kan worden geconcludeerd dat deze markers niet zinvol zijn voor vroegdiagnostiek in SpA. Om deze reden hebben we in hoofdstuk 2 bestudeerd welke biomarkers mogelijk bijdragend zijn bij aan SpA gerelateerde ziekten, namelijk psoriasis en IBD. Uit deze review blijkt dat humaan bèta defensin-2 (hBD-2) en lipocaline-2 bijdragend zouden kunnen zijn, vooral vanuit een pathofysiologisch oogpunt. HBD-2 en lipocaline-2 behoren tot de groep van antimicrobiële peptiden en zijn interessant bij SpA omdat beide peptiden worden gestuurd door interleukine (IL)-17. Uit eerder onderzoek in SpA is gebleken dat het cytokine IL-17 (vanuit de IL-23/IL-17 as) een belangrijke rol speelt bij het ontstaan van SpA. In hoofdstuk 3 hebben wij vervolgens onderzocht of er verschillen zijn in de hBD-2 en lipocaline-2 serumwaardes tussen spondylitis ankylopoetica patiënten en gezonde individuen. Tevens hebben we bekeken of er verschillen zijn in de serumwaardes van IL-27 tussen deze twee groepen, aangezien dit was gerapporteerd in één andere studie. Geen van de drie biomarkers bleek te zijn verhoogd in ons cohort van spondylitis ankylopoetica patiënten in vergelijking met de gezonde individuen. Vanwege deze negatieve resultaten hebben we de experimenten niet meer herhaald in het SPACE cohort met vroege axiale SpA en controle patiënten.
Concluderend kunnen we stellen dat we met gebruik van de bovengenoemde biomarkers voor ontsteking een diagnose van SpA niet kunnen vervroegen.
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Inceptie-cohorten
De inceptie-cohorten vormen een belangrijk onderdeel in het identificeren van klinische, radiologische en biologische markers om SpA in een vroege fase te kunnen opsporen. Een inceptie-cohort is een cohort bestaande uit een groep van individuen met één of meer kenmerken die worden verzameld en vervolgd, bijvoorbeeld om te onderzoeken of zij een bepaalde ziekte ontwikkelen. Wij hebben in hoofdstuk 4 een inceptie-cohort ‘Pre-SpA’ opgezet met ‘op het eerste gezicht gezonde’ eerstegraads familieleden van HLA-B27 positieve spondylitis ankylopoetica patiënten (dit betekent: geen gediagnosticeerde SpA en geen klachten van het bewegingsapparaat waarvoor ze onder behandeling zijn bij huisarts of reumatoloog). Deze groep is gekozen omdat bekend was dat zij een verhoogd risico (12% versus 0,5-1,5% in de gewone populatie) hebben op het ontwikkelen van SpA. De familieleden tussen de 18-40 jaar zullen 5 jaar worden opgevolgd om te evalueren wie uiteindelijk SpA zal ontwikkelen. Deze leeftijdscategorie is gekozen omdat SpA zich voornamelijk manifesteert tussen het 20 en 40e levensjaar. Bij een analyse van de baseline visites van de eerste 51 deelnemers bleek dat 17 (33%) familieleden al konden worden geclassificeerd als hebbende SpA volgens de ASAS axiale SpA en/of de ‘European Spondylarthropathy Study Group‘ (ESSG) criteria. Alhoewel niet alle geclassificeerde deelnemers daadwerkelijk een klinische diagnose zullen hebben (of krijgen), lijkt een aanzienlijk deel van de gezonde eerstegraads familieleden van SpA patiënten toch al klinische manifestaties van SpA hebben die in dit stadium echter nog geen aanleiding waren geweest om een arts te bezoeken, dan wel niet waren herkend horend bij SpA in de praktijk.
Vooralsnog zijn er in elk geval geen biologische markers (CRP, BSE, calprotectine) gevonden die zo’n diagnose kunnen voorspellen. Van de 38 eerstegraads familieleden die niet met SpA geclassificeerd werden, bleek er bij 6 (16%) familieleden tóch sprake te zijn van ontstekingslaesies op de MRI van de SI-gewrichten. Inclusie van meer deelnemers en het langdurig opvolgen van de familieleden zal uitwijzen wie uiteindelijk klinisch manifest SpA zal ontwikkelen. Bovendien kan er dan onderzocht worden of bepaalde markers voorspellend zijn voor het ontwikkelen van SpA.
Het ‘Pre-SpA’ cohort heeft nu reeds een substantieel aantal individuen kunnen classificeren die SpA in de vroege fase van de ziekte zouden kunnen hebben. Na een langere follow-up zal blijken welke klinische, radiologische en biologische markers zouden kunnen bijdragen aan het verkorten van de ‘diagnostic delay’.
HET VOORSPELLEN VAN DE RESPONS OP BEHANDELING
De verschijnselen van SpA kunnen bij een deel van de patiënten goed worden onderdrukt met de huidige medicatie, namelijk NSAIDs en TNF remmers. Maar er zijn een aantal
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beperkingen. Allereerst reageert 40% van de patiënten onvoldoende goed op de ingestelde therapie. Ten tweede kunnen sommige patiënten niet starten in verband met bestaande contra-indicaties of moeten zij na de start alsnog (snel) de behandeling staken in verband met bijwerkingen. Ten derde wordt het proces van botnieuwvorming niet geremd. En ten slotte kan remissie op lange termijn vaak niet worden bereikt: de ziekte vlamt meestal weer op binnen enkele maanden na het staken van TNF blokkade. Anders geformuleerd: de huidige therapieën zijn effectief, maar mede gezien bovengenoemde nadelen, is het belangrijk om nieuwe behandelingen te ontwikkelen. Het is medisch-ethisch niet verantwoord om gedurende langere tijd en op grote schaal patiënten aan klinische trials te laten deelnemen met een gerede kans op een niet-werkende (experimentele) behandeling (of placebo) terwijl er al bewezen effectieve behandelingen bestaan. Een mogelijke oplossing hiervoor is de strategie met de PoC trials, waarbij relatief kort na de start van de behandeling kan worden onderscheiden of een nieuwe behandeling mogelijk effectief zal zijn, dan wel waarschijnlijk ineffectief. PoC trials zijn klinische trials van korte duur met een kleine groepsgrootte. Bij een gunstige uitkomst kunnen grotere fase 2b/fase 3 klinische trials worden gestart voor verdere bewijsvoering.
In hoofdstuk 5 hebben we gekeken naar vroege veranderingen in serum biomarkers vóór en na de start van TNF remmers bij SpA patiënten. Hiervoor zijn een aantal biomarkers geselecteerd, namelijk hoog-sensitief (hs-)CRP, interleukine-6, pentraxine-3, alpha-2-macroglobuline, matrix metalloproteinase-3 [MMP-3], calprotectine en vascular endothelial growth factor [VEGF]). De biomarker serumwaardes zijn gemeten in 3 onafhankelijke SpA cohorten ten tijde van baseline (t=0) en kort na start van behandeling (t=2 of t=4 weken). Gekeken werd bijvoorbeeld of er snelle dalingen (in 2-4 weken tijd) te zien waren in de bloedwaardes in de effectieve groep die niet optraden in de placebogroep. Uit deze analyses bleek dat alleen calprotectine en hs-CRP veranderden tijdens het gebruik van TNF remmers en stabiel bleven in de placebogroep. Vergelijkbare resultaten werden onlangs gevonden bij een nieuw effectief medicament, namelijk secukinumab dat zorgt voor IL-17 blokkade. Dit geeft aan dat deze twee biomarkers niet enkel van potentieel nut kunnen zijn bij het monitoren van het effect van TNF remmers maar mogelijk ook bij medicamenten met een andere ‘mechanism of action’ toepasbaar zijn. De gevoeligheid voor verandering van deze twee (objectieve) biomarkers bleek vergelijkbaar te zijn met die van door de patiënt gerapporteerde uitkomstmaten ‘Bath ankylosing spondylitis disease activity index’ (BASDAI) en de ‘ziekteactiviteit volgens de patiënt’.
Concluderend hebben de calprotectine en hs-CRP biomarkers een hoge gevoeligheid voor verandering bij effectieve therapie op groepsniveau in kleinschalige, kortdurende PoC trials.
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HET IDENTIFICEREN VAN UITKOMSTMATEN
In axiale SpA zijn er diverse uitkomstmaten en dichotome responscriteria ontwikkeld en gevalideerd om het effect van een therapie te kunnen evalueren. In perifere SpA zijn deze maten niet gevalideerd, met uitzondering van artritis psoriatica, waarbij de ‘American College of Rheumatology’ (ACR) en ‘psoriatic arthritis response criteria’ (PsARC) worden toegepast. Een responsmaat ontwikkeld voor perifere SpA is de set van ‘peripheral spondyloarthritis response criteria’ (pSpARC), maar deze index was nog niet uitgebreid gevalideerd. In hoofdstuk 6 hebben we een post-hoc analyse uitgevoerd in twee placebo-gecontroleerde, gerandomiseerde klinische trials met perifere SpA patiënten (n=165 en n=40), waarbij de ene helft van de patiënten de TNF remmer adalimumab ontvingen en de andere helft placebo. Diverse uitkomstmaten werden met elkaar vergeleken. De resultaten tonen dat de scores ‘ziekteactiviteit volgens patiënt´ (patient global) en ´ziekteactiviteit volgens de dokter´ (physician global), globale uitkomstmaten voor meerdere ziektebeelden, alsook de BASDAI en de ‘Ankylosing spondylitis disease activity score’ (ASDAS) indices (gevalideerd voor spondylitis ankylopoietica en toegepast bij axiale SpA), de best discriminerende uitkomstmaten zijn voor klinische trials in perifere SpA. De beste presterende responscriteria zijn de PsPARC en de ACR.
Concluderend hebben de ‘ziekteactiviteit volgens patiënt’ en ‘volgens dokter’, de BASDAI en de ASDAS goede discriminatoire eigenschappen voor het gebruik in klinische trials bij patiënten met perifere SpA. Omdat deze uitkomstmaten natuurlijk in eerste instantie zijn ontwikkeld voor axiale SpA (probleem met ‘face validity’) dienen in de toekomst indices te worden ontwikkeld die meer gericht zijn op symptomen en verschijnselen van perifere SpA. Van de geteste dichotome uitkomstmaten zijn PSpARC en ACR het beste in het discrimineren tussen een succesvolle en niet succesvolle behandeling.
HET VOORSPELLEN VAN STRUCTURELE SCHADE
Structurele schade bij SpA wordt enerzijds gekenmerkt door botdestructie en anderzijds door botnieuwvorming. Botdestructie kan goed worden geremd met TNF blokkade bij perifere SpA (artritis psoriatica). Maar TNF blokkade is niet geschikt om botnieuwvorming bij axiale SpA te remmen. Botnieuwvorming bij axiale SpA kan leiden tot volledige ankylosering van de wervellichamen. Ankylosering leidt tot vermindering van de mobiliteit en functie van de rug en vermindering van kwaliteit van leven. Het voorspellen wie botnieuwvorming en ankylose ontwikkelt, wordt van belang zodra dit proces kan worden afgeremd. Met de huidige therapieën is het nog niet mogelijk het proces af te remmen, maar er zijn aanwijzingen dat bij behandeling in een zeer vroeg ziektestadium dit wellicht wel mogelijk is. Ook zijn er veel therapieën in onderzoek en ontwikkeling, zoals IL-17 blokkade, die mogelijk
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de botnieuwvorming kunnen remmen. Het is dus in toenemende mate van belang inzicht te krijgen in wie de meeste kans heeft op het ontwikkelen van botnieuwvorming opdat adequate behandeling kan worden gestart bij de juiste patiënten (prognostiek). Betere prognostiek leidt ook tot adequate stratificatie voor toekomstige klinische trials gericht op het remmen van botnieuwvorming. De resultaten van hoofdstuk 7 tonen dat serum calprotectine axiale progressie op röntgenfoto’s van de lumbale en cervicale wervelkolom, een radiologische maat voor botnieuwvorming, kan voorspellen. Calprotectine is echter niet beter dan de veelvuldig gebruikte maat CRP, waarvan in een eerder stadium al de voorspellende waarde werd aangetoond.
Concluderend hebben wij in dit proefschrift getracht bij te dragen aan de verbetering van vroegdiagnostiek van SpA en aan het voorspellen van een behandelingsrespons en het optreden van botnieuwvorming. We hebben aangetoond dat onze selectie van inflammatoire biomarkers in serum niet bijdragen aan de vroegdiagnostiek, maar enkele ervan mogelijk wel informatief zijn voor het signaleren van effectieve therapieën in PoC trials en voor het voorspellen van botnieuwvorming bij axiale SpA patiënten. Ten tweede hebben we uitkomstmaten gevalideerd bij perifere SpA. En ten slotte hebben wij het ‘Pre-SpA’ inceptie-cohort opgezet met eerstegraads familieleden van spondylitis ankylopoetica patiënten, waarbij in een aanzienlijk deel van de patiënten SpA kon worden geclassificeerd in een vroeg stadium.
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PHD PORTFOLIO
Name PhD student M.C. Turina
PhD period September 2010 - August 2015General coursesThe Academic Medical Center (AMC) World of Science 2010 0.7 ECTSBasiscursus Regelgeving en Organisatie Klinisch onderzoekers (BROK) AMC 2011 0.9 ECTSPractical Biostatistics AMC 2011 1.1 ECTSScientific Writing in English for Publication AMC 2012 1.5 ECTSClinical Epidemiology AMC 2013 0.6 ECTSCareer Development AMC 2015 0.6 ECTS
Specific coursesFederation of Clinical Immunology Societies (FOCIS) Advance Course in Basic & Clinical Immunology, Scottsdale, USA
2011 1.0 ECTS
American College of Rheumatology (ACR) Basic research pre-conference: bone pathophysiology in inflammatory and rheumatic disorders, Chicago, USA
2011 0.5 ECTS
School of Translational Immunology, the European network for Translational Immunology Research and Education (ENTIRE), Belgrade, Serbia
2012 0.7 ECTS
Postgraduate course Advanced Immunology AMC/VUmc/Sanquin 2012 2.9 ECTSEpidemiology Course of European League Against Rheumatism (EULAR), Berlin, Germany
2013 0.5 ECTS
Seminars and workshops Course Snel lezen Tijdwinst.com 2011 0.2 ECTSCourse Time Management Tijdwinst.com 2011 0.2 ECTSCourse Mind mapping Tijdwinst.com 2011 2.2 ECTSCourse Presence and presentation, MGI coaching 2011 0.2 ECTSWeekly department research seminars AMC 2010-2015 12 ECTSWeekly department clinical education AMC 2010-2013 8 ECTSLecturing Spondyloarthritis preceptorship for Novartis 2012 0.5 ECTSRheumatology introduction course for third year medical students 2012 0.2 ECTS
PresentationsSerum biomarkers to predict clinical response in proof-of-concept trials in spondyloarthritis:European workshop on Immune-Mediated Inflammatory Diseases (ewIMID), Nice, France (poster presentation)
2011 0.5 ECTS
Translational Research Day Institut Pasteur, Paris, France (poster presentation)
2011 0.5 ECTS
ACR/Association of Reproductive Health professionals (ARHP), Annual Scientific Meeting, Chicago, USA (poster presentation)
2011 0.5 ECTS
Efficacy and safety of adalimumab for the treatment of peripheral arthritis in spondyloarthritis patients without ankylosing spondylitis or psoriatic arthritis:
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Nederlandse vereniging voor reumatologie (NVR) Najaarsdagen, Papendal, the Netherlands (oral presentation)
2011 0.5 ECTS
Baseline elevated serum levels of calprotectin as independent marker for radiographic spinal progression in ankylosing spondylitis:European Workshop for Rheumatology Research (EWRR), Prague, Czech (poster tour presentation)
2012 0.5 ECTS
A psychometric analysis of outcome measures in trials of peripheral spondyloarthritis:EULAR Annual European Congress of Rheumatology, Paris, France (poster presentation)
2014 0.5 ECTS
International Congress on Spondyloarthritis, Ghent, Belgium (poster presentation)
2014 0.5 ECTS
Calprotectin (S100A8/A9) as serum biomarker for clinical response in proof-of-concept trials in axial and peripheral spondyloarthritis:EULAR Annual European Congress of Rheumatology, Paris, France (oral presentation)
2014 0.5 ECTS
International Congress on Spondyloarthritis, Ghent, Belgium (poster presentation)
2014 0.5 ECTS
Clinical and imaging signs of spondyloarthritis in first-degree relatives of HLA-B27 positive ankylosing spondylitis patients: the pre-spondyloarthritis (Pre-SpA) cohort:EULAR Annual European Congress of Rheumatology, Rome, Italy (poster tour presentation)
2015 0.5 ECTS
ConferencesewIMID, Sitges, Spain 2010 0.75 ECTSewIMID, Nice, France 2011 0.75 ECTSTranslational Research Day Institut Pasteur, Paris 2011 0.25 ECTSACR/ARHP Annual Scientific Meeting, Chicago, USA 2011 1.5 ECTSNVR Najaarsdagen, Papendal, the Netherlands 2012 0.25 ECTSEWRR Workshop, Prague, Czech 2013 0.75 ECTSEULAR Annual European Congress of Rheumatology, Madrid, Spain 2013 1.0 ECTSEULAR Annual European Congress of Rheumatology, Paris, France 2014 1.0 ECTSInternational congress on Spondyloarthritis, Ghent, Belgium 2014 0.75 ECTSEULAR Annual European Congress of Rheumatology, Rome, Italy 2015 1.0 ECTS
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LIST OF PUBLICATIONS
1 Turina MC*, Ramiro S*, Baeten DL, Mease P, Paramarta JE, Song I-H, Pangan AL, Landewé R. A psychometric analysis of outcome measures in peripheral spondyloarthritis. Ann Rheum Dis 2015;1–6. doi:10.1136/annrheumdis-2014-207235
*equal contributions
2 Vogelpoel LTC, Hansen IS, Rispens T, Muller FJM, van Capel TMM, Turina MC, Vos JB, Baeten DLP, Kapsenberg ML, de Jong EC, den Dunnen J. Fc gamma receptor-TLR cross-talk elicits pro-inflammatory cytokine production by human M2 macrophages. Nat Commun 2014;5:5444. doi:10.1038/ncomms6444
3 Turina MC, Yeremenko N, Paramarta JE, De Rycke L, Baeten D. Calprotectin (S100A8/9) as serum biomarker for clinical response in proof-of-concept trials in axial and peripheral spondyloarthritis. Arthritis Res Ther 2014;16:413. doi:10.1186/s13075-014-0413-4
4 Turina MC, Sieper J, Yeremenko N, Conrad K, Haibel H, Rudwaleit M, Baeten D, Poddubnyy D. Calprotectin serum level is an independent marker for radiographic spinal progression in axial spondyloarthritis. Ann Rheum Dis 2014;73:1746–8. doi:10.1136/annrheumdis-2014-205506
5 Popadic D, Anegon I, Baeten D, Eibel H, Giese T, Marits P, Martinez-Caceres E, Mascart F, Nestle F, Pujol-Borrell R, Savic E, Scheibenbogen C, Seliger B, Thunberg S, Turina M, Villanova F, Winqvist O, Wikström A-C. Predictive immunomonitoring — The COST ENTIRE initiative. Clin Immunol 2013;147:23–6. doi:10.1016/j.clim.2013.01.013
