Comp2 Unit5f Lecture Slides

The Culture of Healthcare

Evidence-Based Practice

Lecture f

This material (Comp2_Unit5f) was developed by Oregon Health and Science University, funded by the Department of Health and Human Services, Office of the National Coordinator for Health Information Technology under Award Number

IU24OC000015.

Evidence-Based PracticeLearning Objectives

• Define the key tenets of evidence-based medicine (EBM) and its role in the culture of health care (Lectures a, b)

• Construct answerable clinical questions and critically appraise evidence answering them (Lecture b)

• Apply EBM for intervention studies, including the phrasing of answerable questions, finding evidence to answer them, and applying them to given clinical situations (Lecture c)

• Understand EBM applied to the other key clinical questions of diagnosis, harm, and prognosis (Lectures d, e)

• Discuss the benefits and limitations to summarizing evidence (Lecture f)

• Describe how to implement EBM in clinical settings through clinical practice guidelines and decision analysis (Lecture g)

2Health IT Workforce Curriculum Version 3.0/Spring 2012

The Culture of Healthcare Evidence-Based Practice

Lecture f

Summarizing Evidence• For many tests and treatments, there are multiple

studies such that one study does not tell the whole story

• As such, there has been a growing trend towards “systematic reviews” or “evidence reports” to bring all the evidence on a treatment or test together

• Per the Haynes 4S model (Haynes, 2001), syntheses bring primary data together while synopses make it available to users in highly digested form

• Summarizing the evidence has many methodogical challenges (Helfand, Morton, Guallar, & Mulrow, 2005)



Lecture f

Steps in Creating a Systematic Review (Guyatt, Rennie, Meade, & Cook, 2008)

• Define the question – population, intervention, comparison, outcome(s)

• Conduct literature search – define information sources and searching strategy

• Apply inclusion and exclusion criteria – for articles retrieved and measure reproducibility

• Abstract appropriate data• Conduct analysis – determine method of

pooling, explore heterogeneity, and assess for publication and other bias



Lecture f

Results From a Systematic Review

• Often use meta-analysis, which combines results of multiple similar studies

• Systematic review ≠ meta-analysis– Studies may be too heterogeneous in terms of patient

characteristics, settings, or other factors, e.g., telemedicine outcomes and diagnosis (Hersh, et al., 2001; Hersh, et al., 2002; Hersh, et al., 2006)

• When meta-analysis is done, summary measures employed usually include odds ratio (OR) or weighted mean difference (WMD)



Lecture f

Usual Meta-Analysis Summary Statistics

• Odds ratio (OR)– Used for binary events, e.g., death, complication, recurrence,

etc.– Usually configured such that OR < 1 indicates treatment

benefit– If CI does not cross OR=1 line, then results are statistically

significant– Can calculate NNT from OR

• Weighted mean difference (WMD)– Used for numeric events, e.g., measurements– Usually configured such that WMD < 0 indicates

treatment benefit– If CI does not cross WMD=0 line, then results are

statistically significant



Lecture f

Systematic Reviews Of Treatment Of Cardiac Risk Factors

• A series of meta-analyses found benefits for lowering cholesterol (Law, Wald, & Rudnicka, 2003) blood pressure (Law, Wald, Morris, & Jordan, 2003), and homocysteine (Wald, Law, & Morris, 2002)

• Leading to a proposal for development of a “polypill” (six medications: statin, three blood pressure lowering drugs in half standard dose, beta blocker, folic acid, and aspirin) that could potentially reduce cardiovascular disease by 80% (Wald & Law, 2003)

• Though a “polymeal” may be natural, safer, and tastier, with wine, fish, dark chocolate, fruits and vegetables, garlic, and almonds (Franco, et al., 2004)

• Initial clinical trial in India found lowering of blood pressure and cholesterol but has not gone on long enough to assess outcomes (Anonymous, 2009)



Lecture f

The Cochrane Collaboration(Levin, 2001)

• An international collaboration with the aim of preparing and maintaining systematic reviews of the effects of health care interventions

• Largest producers of systematic reviews, limited to interventions

• http://www.cochrane.org/



Lecture f

The Cochrane Database Of Systematic Reviews (CDSR)

• “It is surely a great criticism of our profession that we have not organized a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomized controlled trials.”– Archie Cochrane, 1972

• CDSR embodies Cochrane’s vision• About 2,000 reviews done but many more

needed to cover medicine comprehensively



Lecture f

Elements Of Cochrane Reviews

• Statement of clinical problem or question• Sources of evidence

– Literature search– Non-experimental data, if included

• Inclusion/exclusion criteria• Results in tabular and graphical form• Conclusions• Date of last update

– Last update and last substantive update



Lecture f

Other Sources Of Summarized Evidence

• Syntheses – found in• CDSR – www.cochrane.org• Pubmed Health –

http://www.ncbi.nlm.nih.gov/pubmedhealth/• Synopses

– Clinical Evidence – “evidence formulary”– InfoPOEMS – “patient-oriented evidence that

matters”– Physician’s Information and Education Resource

(PIER) from the American College of Physicians

Health IT Workforce Curriculum Version 3.0/Spring 2012


Lecture f11

Limitations Of Systematic Reviews

• Not everyone accepts use of meta-analysis; Feinstein (1995) calls it “statistical alchemy”

• Meta-analyses on same topic sometimes reach different conclusions due to methodologic reasons (Hopayian, 2001)

• “Truth” determined by meta-analysis has the shortest “half life” of all knowledge (Poynard, et al., 2002)

• Effect of publication bias may be exacerbated in systematic reviews (Dickersin, 1997)

Health IT Workforce Curriculum Version 3.0/Spring 2012


Lecture f12

Evidence-Based PracticeSummary - Lecture f

• For many tests and treatments, there are multiple studies such that one study does not give the complete picture

• This has led to the production of “systematic reviews” or “evidence reports” to bring all the evidence on a treatment or test together

• Per the Haynes 4S model, syntheses bring primary data together while synopses make it available to users in highly summarized form.



Lecture f

Evidence-Based PracticeReferences – Lecture f



Lecture f

References Anonymous. (2009). Effects of a polypill (Polycap) on risk factors in middle-aged individuals without cardiovascular

disease (TIPS): a phase II, double-blind, randomised trial. Lancet, 373, 1341-1351. Dickersin, K. (1997). How important is publication bias? A synthesis of available data. AIDS Education and Prevention, 9,

15-21. Feinstein, A. (1995). Meta-analysis: statistical alchemy for the 21st century. Journal of Clinical Epidemiology, 48, 71-79. Franco, O., Bonneux, L., deLaet, C., Peeters, A., Steyerberg, E., & Mackenbach, J. (2004). The polymeal: a more natural,

safer, and probably tastier (than the polypill) strategy to reduce cardiovascular disease by more than 75%. British Medical Journal, 329, 1147-1150.

Guyatt, G., Rennie, D., Meade, M., & Cook, D. (2008). Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. New York, NY: McGraw-Hill.

Haynes, R. (2001). Of studies, syntheses, synopses, and systems: the "4S" evolution of services for finding current best evidence. ACP Journal Club, 134, A11-A13.

Helfand, M., Morton, S., Guallar, E., & Mulrow, C. (2005). Challenges of Summarizing Better Information for Better Health: The Evidence-based Practice Center Experience. Annals of Internal Medicine, 142(12 - Part 2).

Hersh, W., Helfand, M., Wallace, J., Kraemer, D., Patterson, P., Shapiro, S., & Greenlick, M. (2001). Clinical outcomes resulting from telemedicine interventions: a systematic review. BMC Medical Informatics and Decision Making, 1, 5. Retrieved from http://www.biomedcentral.com/1472-6947/1/5

Hersh, W., Helfand, M., Wallace, J., Kraemer, D., Patterson, P., Shapiro, S., & Greenlick, M. (2002). A systematic review of the efficacy of telemedicine for making diagnostic and management decisions. Journal of Telemedicine and Telecare, 8, 197-209.

Hersh, W., Hickam, D., Severance, S., Dana, T., Krages, K., & Helfand, M. (2006). Diagnosis, access, and outcomes: update of a systematic review on telemedicine services. Journal of Telemedicine & Telecare, 12(Supp 2), 3-31.

Evidence-Based PracticeReferences – Lecture f (continued)

References (continued)Hopayian, K. (2001). The need for caution in interpreting high quality systematic reviews. British Medical Journal, 323,

681-684. Law, M., Wald, N., Morris, J., & Jordan, R. (2003). Value of low dose combination treatment with blood pressure

lowering drugs: analysis of 354 randomised trials. British Medical Journal, 326, 1427-1431. Law, M., Wald, N., & Rudnicka, A. (2003). Quantifying effect of statins on low density lipoprotein cholesterol, ischaemic

heart disease, and stroke: systematic review and meta-analysis. British Medical Journal, 326, 1423-1427. Levin, A. (2001). The Cochrane Collaboration. Annals of Internal Medicine, 135, 309-312. Poynard, T., Munteanu, M., Ratziu, V., Benhamou, Y., Martino, V. D., Taieb, J., & Opolon, P. (2002). Truth survival in

clinical research: an evidence-based requiem? Annals of Internal Medicine, 136, 888-895. Wald, D., Law, M., & Morris, J. (2002). Homocysteine and cardiovascular disease: evidence on causality from a meta-

analysis. British Medical Journal, 325, 1202-1206. Wald, N., & Law, M. (2003). A strategy to reduce cardiovascular disease by more than 80%. British Medical Journal,

326, 1419-1423.



Lecture f

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