Evidence-based medicine, part 3. An introduction to critical appraisal of articles on diagnosis.

This article provides an introductory step-by-step process to appraise an article on diagnosis. The authors introduce these principles using a systematic approach and case-based format. The process of assessing the validity of an article on diagnosis, determining its importance, and applying it to an individual patient is reviewed. The concepts of study population homogeneity, reference and criterion standards, and completeness are discussed to help physicians determine an article's validity. Instruction on calculating prevalence, sensitivity, specificity, and positive and negative predictive values and likelihood ratios is provided and applied to a hypothetical clinical scenario. Study generalizability and the role of patient values, expectations, and concerns are also addressed. The skills learned from appraising an article on diagnosis in the manner outlined provides a solid basis for life-long learning and improved patient care.