How should health care professionals choose among the many therapies claimed to be efficacious for treating specific disorders? The practice of evidence-based medicine provides an answer. Advocates of this approach urge health care professionals to base treatment choices on the best evidence from systematic research on both the efficacy and adverse effects of various therapeutic alternatives. Ideally, health care professionals would compare different treatments by referring to randomized, double-blind, head-to-head trials that compared the treatment options. Although individual medications are typically well researched when these placebo-controlled studies are performed, studies that directly compare treatments are rare. In the absence of direct head-to-head trials, other evidence comes from indirect comparisons of two or more therapies by examining individual studies involving each treatment.

This article provides an introductory review of methods of such indirect comparisons of therapies across studies, provides examples of how these methods can be used to make treatment decisions, and presents a general overview of relevant issues and statistics for readers interested in understanding these methods more thoroughly.