Post on 06-Jan-2022
transcript
Gary R Lichtenstein, MD Professor of Medicine
Director, IBD Center
University of PA School of Medicine
Philadelphia, PA
Diagnostic Markers in IBD
Diagnosing and Classifying IBD
Can be Challenging
• Large degree of overlap in clinical symptoms with other GI diseases
• Clinical symptoms don’t always correlate with disease activity and severity of inflammation
• Clinical indices (e.g., CDAI, HBI) are subjective and don’t correlate well with endoscopic findings and serum markers of inflammation
• Endoscopic imaging can’t detect transmural inflammation or penetrating disease
• Pathology assessment is often nonspecific
Distinguishing UC from CD is
Not Always Straightforward
Distribution Continuous, symmetric, and
diffuse distribution
Distribution is often discontinuous and
asymmetric with skipped segments and normal
intervening mucosa
Depth of Inflammation Mucosal/submucosal inflammation Mucosal, submucosal, and/or transmural
inflammation
Site Colon affected exclusively May affect any part of GI tract
Rectal Involvement Almost always involves
the rectum
Relative rectal sparing may be present
Ulcerative Colitis Crohn’s Disease
Multiple Tools are Typically Used to
Establish a Diagnosis
Stool cultures
Colonoscopy, Endoscopy
Crohn’s
Disease
Ulcerative
Colitis
Fletcher JG et al. Gastroenterology. 2011;140:1795–1806.
Benefits and Risks of Imaging Tests in IBD
Imaging Test Benefits Risks
CT enterography
(CTE)
• Detection of clinically occult inflammatory and
penetrating disease
• Complementary to ileocolonoscopy
• Images entire abdomen/pelvis
• Temporal and spatial resolution > MRE
• Widely available technology and expertise
• Radiation
• Iodine dye (renal
insufficiency, allergy)
• Cannot detect
colonic neoplasia
MR enterography
(MRE)
• Detection of clinically occult
inflammatory and penetrating
disease
• Complementary to ileocolonoscopy
• Images entire abdomen/pelvis
• Lack of radiation
• Image quality may be
suboptimal in some
patients
• Cannot detect
colonic neoplasia
Iliocolonoscopy (Ico)
• Best test for detection of colonic inflammation
• Histologic sampling
• Synchronous neoplasia surveillance
• Can assess mucosal healing
• Perforation
• Limited bowel evaluation
• Cannot stage
penetrating disease
Chromeondoscopy • improved detection of intraepithelial neoplasia compared to
surveillance colonoscopy
Capsule Endoscopy • Most sensitive for detecting small bowel mucosal
inflammation (other than double balloon)
• Retention
Inflammatory Bowel Disease
Genetics Has Made Great Progress
Prior 2005 2006 2007 2008
TNFSF15 ATG16L1
IL23R
ZNF365
PTGER4
IRGM
MST1
ECM1 C11orf30
JAK2
CCR6
CDKAL1
IL12B
PTPN22
ORMDL3
STAT4
ICOSLG
10p11
8q24
7p12
6q21
1q32
STAT3
13q14
19p13
21q21
MHC
5q31
NOD2
NKX2-3
ITLN1
LRRK2/MUC19
Barrett JC et al. Nat Genet. 2008;40:955-962.
Genes Associated with IBD, CD, and UC
Thompson AI and Lees CW. Inflamm Bowel Dis. 2011;17:831-848.
ATG16L1 – The Autophagy Gene
• Constitutive process for regulating
intracellular homeostasis and removal
of intestinal microbes
• Critical pathway for the breakdown of
bacteria: E coli, Salmonella, Legionella,
M tuberculosis
• ATG16L1 mutations are associated
with CD
– P=2.33 X 10-7
Bacterial Clearing1-6
1. Parkes M et al. Nat Genet. 2007;9: 830-832; 2. Yamazaki K et al. J Hum Genet. 2007;52:575-583; 3. Prescott NJ et al. Gastroenterology.
2007;132:1665-1671; 4. Rioux JD, et al. Nat Genet. 2007;39:596-604; 5. Hampe J et al. Nat Genet. 2007;39: 207-211; 6. Cummings JR et al. Inflamm
Bowel Dis. 2007:13-18
ECM1: The UC Susceptibility Gene
• Related to intestinal barrier function
• Plays a role in epithelial cell interactions
• Mutations are associated with increased mucosal layer permeability
• P=2.3 x 10-6 in UC
UC Susceptibility Gene
GWA=genome-wide association; MHC=major histocompatibility complex
1. Thompson AI and Lees CW. Inflamm Bowel Dis. 2011;17:831-848; 2. Fisher SA et al Nat Genet. 2008;40:710-712.
STAT3 – Proinflammatory Mediator
• Signal transduction and activator of transcription
• Activated STAT3 is necessary for the signaling of pro-inflammatory cytokines in IBD
• Plays a role in the biology of Th17 cells
• P=9.15x10-8 in CD
Proinflammatory Mediator1,2
1. Jarnicki A et al. Cell Division. 2010;5:14; 2. Barret JC et al. Nat Genet. 2008;40:955-962.
NKX2-3 – Transcription Factor
• Transcription factor implicated in cell type specification and maintenance of differentiation
• Expressed in endothelial cells and intestinal lamina propria mesenchymal cells
• Associated with both UC and CD
• CD P=.009; UC P=.001
Transcription Factor
Meggyesi A et al. World J Gastroenterol. 2010;16:5233-5240.
Genetic Markers
Marker General
Prevalence Role/Function Effect
ATG16L1
(associated
with CD)1-6
OR 1.45 • Elongates membranes that form
autophagosomes in autophagy
• May decrease ability to remove
intestinal microbes
• Increases production of
inflammatory cytokines from macrophages
ECM1
(associated
with UC)7,8
OR 1.3 – 1.4 • Interacts with basal membrane,
inhibits MMP9 proteins, and
activates signaling of
proinflammatory cytokine
pathway NF-kB
• Exhibits defective barrier function
• Causes thickening and scarring of mucus
membranes
NKX2.3
(associated with
CD and UC)9
OR 1.2 – 1.6 • Encodes transcription factor that
functions in cell specification and
maintenance of tissue differentiation
• Associated with defects in gut development,
abnormal tissue architecture, abnormalities
in migration and segregation of B and T
cells
STAT3
(associated with
CD and UC)10-11
OR 1.18 • Plays role in the Th17-dependent
autoimmune process
• Expansion and overactivity on Th17 helper
cell cytokines can lead to intestinal
inflammation
OR=odds ratio
1. Parkes M et al. Nat Genet. 2007;9: 830-832; 2. Yamazaki K et al. J Hum Genet. 2007;52:575-583; 3. Prescott NJ et al. Gastroenterology.
2007;132:1665-1671; 4. Rioux JD, et al. Nat Genet. 2007;39:596-604; 5. Hampe J et al. Nat Genet. 2007;39: 207-211; 6. Cummings JR et al. Inflamm
Bowel Dis. 2007:13-18; 7. Thompson AI and Lees CW. Inflamm Bowel Dis. 2011;17:831-848; 8. Fisher SA et al Nat Genet. 2008;40:710-712; 9.
Meggyesi A et al. World J Gastroenterol. 2010;16:5233-5240; 10. Jarnicki A et al. Cell Division. 2010;5:14; 11. Barret JC et al. Nat Genet.
2008;40:955-962.
Role of Angiogenesis in IBD
• Serum concentrations are significantly increased in active CD and UC patients compared to those with quiescent disease or healthy controls
• Serum levels correlate with disease activity
– Increased intramural blood flow
– Higher production rates in inflamed mucosa of active CD and UC patients vs normal mucosa of healthy controls
• Induces epithelial cell migration which can play a role in intestinal cell restitution
VEGF
Koutroubakis D et al. Inflamm Bowel Dis. 2006;12:515-523.
Role of Adhesion Molecules in IBD
• Unregulated in response to inflammation in both CD and UC patients
• Facilitate adhesion and infiltration of leukocytes into the inflammation site
• Correlate with disease activity in IBD patients
• Play an important role in colitis associated angiogenesis
ICAM-1, VCAM-1
Chidlow et al., Am J Physiol Gastrointest Liver Physiol 2007, 293: G5–G18
Inflammatory Markers Correlate
with Disease Activity
• Produced in the liver in response
to inflammation
• Can be used to differentiate IBD
from functional bowel diseases
• Stronger response in CD patients
vs UC patients and in colonic vs.
small intestinal disease
• CRP levels at the time of
diagnosis are related to the
extent of disease
• 20%-30% of patients cannot
mount a CRP response
• Produced in the liver in response
to inflammation
• Physiologic levels are ~10x
higher than that of CRP
– Allows for easier detection
of slight elevations
• Similarly elevated in both CD
and UC
CRP SAA
CRP=C-reactive protein; SAA=serum amyloid A
Inflammatory Bowel Disease
Test Development
Objectives:
• To identify a set of blood-based immune, genetic, and inflammatory biomarkers that could be used to improve the identification of IBD patients and differentiation between CD and UC over that in the existing IBD Serology 7 test
• Develop the next generation IBD diagnostic test using a representative and well-characterized cohort of IBD, GI disease and healthy control samples
Plevy SE et al. DDW 2012. Abstract no. 166
Well-characterized samples with known diagnoses from
8 academic and 42 community centers in North America
Training and Validation Cohorts
Disease Diagnosis Training Cohort
n (%)
Validation Cohort
n (%)
Crohn’s Disease 419 (39) 153 (35)
Ulcerative Colitis 227 (21) 101 (23)
GI Controls 314 (29) 123 (28)
Healthy Controls 123 (11) 60 (14)
Total 1083 (100) 437 (100)
Plevy SE et al. DDW 2012. Abstract no. 166
Serology, Genetics, and Inflammation Markers
s • ASCA-A
• ASCA-G
• anti-OmpC
• anti-CBir-1
• anti-A4-Fla2
• anti-FlaX
• ANCA
• pANCA-IFA
• pANCA DNAse
g • ATG16L1
• ECM1
• NKX2-3
• STAT3
i • ICAM1
• VCAM1
• VEGF
• CRP
• SAA
Plevy SE et al. DDW 2012. Abstract no. 166
ROC Curves for Individual Markers Marginal Discrimination: IBD vs. non-IBD
ROC=receiver-operator curve
Plevy SE et al. DDW 2012. Abstract no. 166
Higher Level of Discrimination:
IBD vs Non-IBD
Plevy SE et al. DDW 2012. Abstract no. 166
IBD sgi Performs Better than IBD 7
in Differentiating CD vs UC
In a head-to-head
comparison, IBD sgi
demonstrated improved
overall performance over
IBD Serology 7 in
differentiating CD vs UC
Absolute
Improvement
Relative
improvement
CD /
UC (AUC)
15% 19%
Plevy SE et al. DDW 2012. Abstract no. 166335
Overall Diagnostic Performance IBD sgi vs. IBD Serology 7
In a head-to-head comparison of diagnostic performance,
IBD sgi demonstrated absolute and relative improvements
over IBD Serology 7
IBD sgi IBD Serology 7 Absolute
Improvement
Relative
Improvement
IBD vs. Non-IBD
(AUC) 0.87 0.80 7% 9%
CD / UC
(AUC) 0.93 0.78 15% 19%
Plevy SE et al. DDW 2012. Abstract no. 166
IBD sgi Performance Characteristics
74%
89%
98%
90%
81% 84%
0%
20%
40%
60%
80%
100%
IBD CD UC
Sensitivity Specificity
Plevy SE et al. DDW 2012. Abstract no. 166
Diagnosis Predictive
Values High Pre-test Probability
IBD
PPV 98%
NPV 37%
CD
PPV 96%
NPV 56%
UC
PPV 97%
NPV 87%
Low Pre-test Probability
56%
95%
45%
98%
52%
100%
Test Performance by Pre-test Probability
Med. Pre-test Probability
88%
77%
82%
88%
86%
97%
NPV=negative predictive value; PPV=positive predictive value
Plevy SE et al. DDW 2012. Abstract no. 166
Potential Benefits of an Accurate IBD Diagnosis
Early disease (mild-moderate
disease)
Advanced disease
(moderate-severe disease)
Prevention of
complicated disease
Selection of appropriate
management strategies
Conclusions
• The pathogenesis of IBD reflects dysregulated immunologic responses to diverse antigens (yeast, bacteria, flagellins, auto-antibodies) in a genetically susceptible person resulting in inflammation and tissue injury
• A random Forest model that analyzes the complex interactions between the 3 classes of markers (serology, genetics, inflammation) is more accurate at detecting patterns that differentiate IBD vs non-IBD and CD vs UC patients than using a single class of markers (serology)