Meta-analysis of clinical trials: a consumer's guide.

Meta-analysis is a popular statistical tool allowing the synthesis of related research studies in a quantitative manner. Components of a good meta-analysis are first discussed, with a view toward critical reading of reports of meta-analyses. Examples include lipid-lowering drugs and coronary artery bypass graft surgery. A role for meta-analysis in the design and monitoring of clinical trials was examined at a workshop held at the National Institutes of Health and aspects of these uses of meta-analyses are considered. Basic analytical and graphical methods of meta-analysis are briefly reviewed. The goal is to encourage more thoughtful evaluation of the many meta-analyses that are published or are presented.