comp2 unit5e lecture slides

The Culture of Healthcare

Evidence-Based Practice

Lecture eThis material (Comp2_Unit5e) 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 PracticeObjectives

• 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 e

Using EBM To Assess Questions About Harm Or Etiology

• Question is not whether someone with exposure to agent gets ill, but rather those with illness have higher rate or amount of exposure

• Ideally assessed by RCT but this may be impractical or unethical

• Next best evidence comes from observational studies, which have limitations



Lecture e

Examples Of Questions To Answer About Harm

• Do silicone breast implants cause autoimmune diseases, such as lupus? (Gabriel, et al., 1994)– Women with silicone breast implants developed

connective tissue diseases and arthritis but at no higher rate than those without them

• Do anti-obesity drugs (e.g., fenfluramine and phentermine, also known as fen-phen) cause heart valve abnormalities? (Gardin, et al., 2000)– Those who used these drugs developed certain heart

valve abnormalities at a higher rate than those who did not



Lecture e

Hierarchy Of Evidence For Harm

• Randomized controlled trial• Cohort study• Case control study• Case series/report



Lecture e

Evidence And Its Limits

• Randomized controlled trial– Ideal, but often cannot be done or would be unethical

to do so• Cohort study

– Prospective study without randomization– Is particularly useful when poor outcomes are rare

and huge sample size would be required, e.g., upper gastrointestinal hemorrhage with NSAIDs

– Are problematic when groups are really not similar, e.g., people who take NSAIDS may be sicker or otherwise different than those who do not



Lecture e

Evidence And Its Limits (continued)

• Case control study (continued)– Most common form of observational study– Retrospectively identify cases of diseases and

match to otherwise similar controls, looking to see if different rate or amount of exposure

– Can be useful when condition is very rare or has long development time

• Classic case was demonstration that DES causes vaginal cancer (reviewed in Swan, 2000)



Lecture e


• Case control study (continued)– Problem is when controls create spurious

association, e.g.,• Coffee drinking associated with pancreatic cancer

(MacMahon, Yen, Trichopoulos, Warren, & Nardi, 1981), but controls were patients with other GI diseases whose symptoms were exacerbated by coffee (so they drank less)

• Differences were not present when other appropriate controls were used (Zheng, et al., 1993)



Lecture e


• Case series/report– No comparison group– Famous example was Bendectin for nausea in

pregnancy, where adverse publicity led to removal from market of safe and effective treatment

• Actually was combination of two agents, both of which were effective and neither of which were harmful (Magee, Mazzotta, & Koren, 2002)



Lecture e

“Pure” Prognosis Studies Are Rare

• Prognosis is “natural history” of disease• But very little “history” is “natural” in modern era

with our abundance of diagnostic tests, interventions, harmful agents, etc.

• Many studies measure prognosis after a test or intervention



Lecture e

Prognosis Usually Measured By A Survival Curve

5.5 Chart: Survival Curve (Adapted from Dunn, 2002)



Lecture e

Example Studies Of Prognosis• Extremely pre-term birth (Marlow, Wolke, &

Bracewell, 2005)– Followed cohort of 241 children from UK and Ireland

born at 25 or fewer weeks gestation– Compared with 160 classmates born at full-term– 41% of pre-term children had “serious impairment” on

cognitive assessment compared with 1.3% in control group

• Untreated early, localized prostate cancer (Johansson, et al., 2004)– 223 men followed from 1977-1984– 17% developed generalized disease– 16% died of disease



Lecture e

Evidence-Based PracticeSummary – Lecture e

13

• Questions about harm assess whether exposure to some natural or manmade agent causes disease and is usually answered with a case-control study

• Questions about prognosis tell us the natural course of disease

Health IT Workforce Curriculum Version 3.0/Spring 2012


Lecture e

Evidence-Based Practice References – Lecture e



Lecture e

References Gabriel, S., O'Fallon, W., Kurland, L., Beard, C., Woods, J., & Melton, L. (1994). Risk of connective-tissue diseases

and other disorders after breast implantation. New England Journal of Medicine, 330, 1697-1702. Gardin, J., Schumacher, D., Constantine, G., Davis, K., Leung, C., & Reid, C. (2000). Valvular abnormalities and

cardiovascular status following exposure to dexfenfluramine or phentermine/fenfluramine. Journal of the American Medical Association, 283, 1703-1709.

Johansson, J., Andren, O., Andersson, S., Dickman, P., Holmberg, L., Magnuson, A., & Adami, H. (2004). Natural history of early, localized prostate cancer. Journal of the American Medical Association, 291, 2713-2719.

MacMahon, B., Yen, S., Trichopoulos, D., Warren, K., & Nardi, G. (1981). Coffee and cancer of the pancreas. New England Journal of Medicine, 304, 630-633.

Magee, L., Mazzotta, P., & Koren, G. (2002). Evidence-based view of safety and effectiveness of pharmacologic therapy for nausea and vomiting of pregnancy (NVP). American Journal of Obstetrics and Gynecology, 186, S256-S261.

Marlow, N., Wolke, D., & Bracewell, M. (2005). Neurologic and developmental disability at six years of age after extremely preterm birth. New England Journal of Medicine, 352, 9-19.

Swan, S. (2000). Intrauterine exposure to diethylstilbestrol: long-term effects in humans. Acta Pathologica, Microbiologica et Immunologica Scandinavica, 108, 793-804.

Zheng, W., McLaughlin, J., Gridley, G., Bjelke, E., Schuman, L., Silverman, D., . . . Fraumeni, J. (1993). A cohort study of smoking, alcohol consumption, and dietary factors for pancreatic cancer (United States). Cancer Causes & Control: CCC, 4, 477-482.

Charts, Tables, Figures 5.5 Chart: Survival Curve, Adapted from Dunn, S. (2002). Survival Curves: The Basics: CancerGuide.

comp2 unit5e lecture slides

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