The rationale behind systematic reviews in clinical medicine: a conceptual framework.

A systematic review (SR) is a type of review that uses a systematic method to provide a valid summary of existing literature addressing a clear and specific question. In clinical medicine (CM), the concept of SR is well recognized, especially after the introduction of evidence-based medicine; The SR of randomized clinical trials (RCTs) is considered the highest level of evidence on therapeutic effectiveness. Despite the popularity of the SRs and the increasing publication rate of SRs in CM and other healthcare literature, the concept has raised criticisms. Many of proper criticisms can be due to the deviation of some existing SRs from the original philosophy and well-established rationale behind the concept of SR. On the other hand, many criticisms are misconceptions about SRs which still exist even several decades after introducing the concept. This article presents a conceptual framework for clarifying the rationale behind SR in CM by providing the relevant concepts and their inter-relations, explaining how methodological standards of an SR and its rationale are connected, and discussing the rationale under the three-section: SR as a type of synthetic research, SR as a more informed and less biased review, and SR as an efficient scientific tool.