Evidence-Based Medicine Week 3 - Prognosis Department of Medicine - Residency Training Program Tuesdays, 9:00 a.m. - 11:30 a.m., UW Health Sciences Library

Steps in Practicing EBM 1.Convert the need for information into an answerable question. 2.Track down the best evidence with which to answer that question. 3.Critically appraise the evidence for its validity, impact, and applicability. 4.Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

Review Last Week’s Session

Weeks 3 & 4 - Prognosis “Fourth, despite its importance in clinical decision making, prognosis gets short shrift relative to research in diagnosis or treatment. In 2005 to 2006, the editors hope to publish more papers that give clinicians and their patients useful information about prognosis. We are most interested in articles that highlight important clinical outcomes and how frequently such outcomes occur; that provide precise estimates of how well prognostic indicators predict important outcomes; and that communicate this information so that clinicians can easily understand and use it. We also welcome systematic reviews that clearly describe limitations of current knowledge about prognosis, that summarize information that would be useful for patients with particular prognostic findings, and that provide clinicians with a meaningful template for sharing prognostic information with their patients.” Excerpted from: The Editors. Annals A peak back and a look forward. Ann Intern Med. 2005;142:

Steps in Practicing EBM 1.Convert the need for information into an answerable question. 2.Track down the best evidence with which to answer that question. 3.Critically appraise the evidence for its validity, impact, and applicability. 4.Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

The Answerable Question

Good questions are the backbone of practicing EBM. It takes practice to ask the well-formulated question.

Well-Built Clinical ?’s Directly relevant to the care of the patient and our knowledge deficit. Contains the following elements: –the patient or problem being addressed –the intervention or exposure being considered –the comparison intervention or exposure, when relevant –the clinical outcomes of interest.

Well Formulated ?’s Focus scarce learning time on evidence directly relevant to patient’s needs and our particular knowledge needs. Suggest high-yield search strategies. Suggest forms that useful answers might take. Help us to model life-long learning techniques for our colleagues and students. Are answerable and, thus, reinforce the satisfaction of finding evidence that makes us better, faster clinicians.

Prognosis Questions

Steps in Practicing EBM 1.Convert the need for information into an answerable question. 2.Track down the best evidence with which to answer that question. 3.Critically appraise the evidence for its validity, impact, and applicability. 4.Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

Resources META-SEARCH ENGINES PrimeAnswers TRIP+ SUMSearch SYSTEMATIC REVIEWS/META-ANALYSES Cochrane Library PubMed Clinical Queries using Research Methodology Filters EVIDENCE GUIDELINES/SUMMARIES AHRQ Evidence Reports Clinical Evidence AHRQ Preventive Services CLINICAL RESEARCH CRITIQUES ACP Journal Club Bandolier BestBETs CASE REPORTS/SERIES, PRACTICE GUIDELINES, ETC National Guideline Clearinghouse PubMed

Steps in Practicing EBM 1.Convert the need for information into an answerable question. 2.Track down the best evidence with which to answer that question. 3.Critically appraise the evidence for its validity, impact, and applicability. 4.Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

Strategies for Critical Appraisal of Studies on Prognosis Clinical Importance Validity Applicability

Strategies for Critical Appraisal of Studies on Prognosis Validity

Are The Results Valid? 1. Assembled a defined, representative sample of patients at a common point in course of disease. 2. Follow-up of patients sufficiently long and complete. 3. Objective outcome criteria applied in a “blinded” fashion. 4. If subgroups with different prognosis: - Adjustment for other important prognostic factors. - Validation of an independent group of “test-set” patients.

Types of Studies Most studies will be “cohort studies”. RCT’s (particularly placebo arms) can generate information about prognosis of disease. Case-control studies can be useful but fail to provide estimates of absolute risk. Mostly encountered when the outcome is rare or required duration of follow-up is long.

The Cohort of Patients How close to “ideal” does the study come in terms of how the disease was defined and how the participants were assembled (“full spectrum of illness”). –e.g. avoid “referral bias” if possible Is this an “inception” cohort or is there uniform entry point (for late stage disease)? start smokingatherosclerosislung cancerdeathstart smokingatherosclerosislung cancerdeath smoking cessation program

Follow-up To know if length of follow-up sufficient often requires general knowledge about disease. Complete follow-up is critical. Failure is influenced both by better than average and worse than average clinical course. –“ 5% and 20%” rule. –worst-case scenario/sensitivity analysis

Outcome Criteria Extreme outcomes are easy to recognize. Outcomes in between require judgement and thus require standard criteria. Those making judgement are kept “blind” to patients’ clinical characteristics and prognostic factors.

Adjustment and Validation If subgroups with different prognosis then was there statistical adjustment for other important prognostic factors (statistical adjustment is not explanatory). To the extent that adjustment is not explanatory, the first time a prognostic factor is identified, is there a confirmatory data set of patients (“derivation set” and “validation sets”).

Strategies for Critical Appraisal of Studies on Prognosis Clinical Importance

Clinically Important? 1. How likely are the outcomes over time? 1. Percentage “survival” at a particular point in time. 2. Median survival. 3. Survival curves. 2. How precise are the prognostic estimates? 95% CI - range of values within which we can be 95% sure that the population value lies

Survival Curves 1 year survival 95% Median survival unknown 1 year survival 20% Median survival 3 months 1 year survival 20% Median survival 9 months 1 year survival 20% Median survival 7 months

Strategies for Critical Appraisal of Studies on Prognosis Applicability

Applicable to Our Patient? 1. Are the study patients similar to our own? 2. Will the evidence make a clinically important impact on our conclusions about what to offer or tell our patient?

Questions? Start Searching!