The Evidence Based Medicine approach to diagnostic testing: practicalities and limitations.

Evidence-Based Medicine (EBM) has become a popular approach to medical decision making and is increasingly part of undergraduate and postgraduate medical education. EBM follows four steps: 1. formulate a clear clinical question from a patient's problem; 2. search the literature for relevant clinical articles; 3. evaluate (critically appraise) the evidence for its validity and usefulness; 4. implement useful findings into clinical practice. This review describes the concepts, terminology and skills taught to attendees at EBM courses, focusing specifically on the approach taken to diagnostic questions. It covers how to ask an answerable clinical question, search for evidence, construct diagnostic critically appraised topics (CATs), and use sensitivity, specificity, likelihood ratios, kappa and phi statistics. It familiarises readers with the lexicon and techniques of EBM and allows better understanding of the needs of EBM practitioners.