Issues in subgroup analyses and meta-analyses of clinical trials

This commentary discusses two techniques commonly used to analyze clinical trials: subgroup analysis and meta-analysis. Subgroup analysis is used to evaluate the consistency of a treatment across multiple groups, usually within a clinical trial. Subgroup analysis often is used to generate or test an hypothesis about risk factors or treatment responses. Meta-analysis (overview) is used primarily to summarize data from several randomized clinical trials and to evaluate consistency among trials. Meta-analysis is a formal way of summarizing the totality of information coming from well-conducted randomized clinical trials. The use and limitations of these two techniques are discussed.