Evidence-Based Practice and Critical Appraisal
The EBP process
Evidence-based practice questions test the ability to formulate a focused question, search efficiently, appraise validity, and apply evidence to a specific patient. Know study designs: randomized controlled trials for therapy, cohort and case-control for prognosis and harm, diagnostic accuracy studies for tests, and systematic reviews for synthesis. Understand bias, confounding, confidence intervals, and the difference between statistical and clinical significance.
Traps in question stems
Common traps include accepting a single study as definitive, confusing association with causation, and ignoring applicability to the patient in front of you. Questions may test whether a p-value or confidence interval supports a claim. Another trap is the answer that cites the newest technology rather than the best evidence. Watch for questions about levels of evidence and GRADE-style certainty.
Rule of thumb
Use the "PICO" rule: Population, Intervention, Comparison, Outcome. If a study does not match your patient's population or outcome, its applicability is limited regardless of its internal validity.
Worked example
A systematic review shows a statistically significant but tiny improvement in bond strength with a new adhesive. Clinically, the difference may be irrelevant. The examinable answer weighs clinical significance and applicability, not just the p-value.