What Is Evidence-Based Medicine?

Evidence-based medicine (EBM) is the conscientious, explicit and judicious use of the best current evidence in making decisions about the care of individual patients, integrated with clinical expertise and patient values. It does not mean "follow randomised trials blindly" or "ignore experience".

The three components

1. Best available research evidence, appraised for quality.
2. Clinical expertise, including the ability to assess the patient's condition and context.
3. Patient values and preferences.

The five steps

1. Ask an answerable question (the PICO format; see What Is the PICO Framework?).
2. Acquire the best evidence with a reasoned search.
3. Appraise its validity, results and applicability.
4. Apply it to the patient in front of you.
5. Assess how it went, and learn from it.

Hierarchy of evidence, with caveats

Systematic reviews of randomised trials usually sit at the top for questions about treatment effects, followed by single randomised trials, cohort studies, case-control studies and case reports. The best design depends on the question: for prognosis or harm, a cohort study may be most informative. Certainty can be downgraded (risk of bias, inconsistency, imprecision) or upgraded; GRADE is one structured approach. See How to Use GRADE to Assess Certainty of Evidence.

Illustrative example

Invented for teaching. A clinician asks: "In adults with atrial fibrillation (P), does anticoagulation (I) versus no anticoagulation (C) reduce stroke (O)?" She finds a recent systematic review, checks its quality, notes that the trial participants were younger than her 88-year-old patient, discusses bleeding risk and preferences with the patient, and decides together with the patient.

Common pitfalls

• Treating the hierarchy as a rigid rule.
• Ignoring whether study participants resemble your patient.
• Using evidence without considering patient preferences.

Key takeaways

• EBM integrates evidence, expertise and patient values.
• Appraisal and applicability matter as much as finding a study.

This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.