Critical appraisal of medical literature: an aid to rational decision making

Clinical decisions should be based on evidence. This paper explores the skills necessary to read critically and evaluate medical literature, and in particular discusses how to appraise a study from a general practice perspective. It outlines the different types of study used in medical literature and the weight that should be attributed to each. The anatomy of a research paper is described indicating the important features to be found in each section of a study; the Introduction, Methods, Results, Discussion and Conclusion (IMRAD) and the essential components, possible problems, and sources of bias that may be found in each section. The need for close examination of the methodology is emphasised, as this determines the quality of the study, with sufficient detail provided in the methods section that the study could be replicated. Sampling and bias are explored in detail and the important features of a measuring instrument are described. Response rates, confounding factors and the use of statistics are also highlighted. The study upon which the research paper is based is usually the best that was possible within resource limitations and, while the evidence should be appraised objectively, the quality of the study should be seen within the context of these limitations.