Towards evidence-based diagnosis in developing countries: the use of likelihood ratios for robust quick diagnosis

Evidence-based medicine (EBM), a relatively new paradigm for clinical practice, stresses the use of research evidence in diagnostic evaluations and therapeutic interventions. Financial and instrumental scarcities in developing countries require cliniciansto visit patients under time constraints, especially in outpatient clinical settings. In this situation, clinicians need diagnostic approaches that reduce both diagnostic time and errors. This article discusses what EBM can do to help physicians in this regard. For quick history taking and physical examination, all physicians utilize certain "key pointers" (signs or symptoms or paraclinical tests that influence the pretest estimation of the disease prevalence). EBM emphasizes that these key pointers are nothing but signs or symptoms with significant likelihood ratios. Likelihood ratios are a practical means of interpreting clinical tests; physicians can derive likelihood ratios from critically appraised studies. The use of clinical tests with sizeable likelihood ratios and with likelihood ratios for key pointers from independent body systems may significantly decrease both diagnostic time and errors. EBM could be a significant aid to physicians in the developing world.