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Systematic review and meta-analysis

Ethan Balk, MD, MPH
Peter A L Bonis, MD
Section Editor
Joann G Elmore, MD, MPH
Deputy Editor
Carrie Armsby, MD, MPH


Clinical decisions in medicine ideally should be based upon guidance from a comprehensive assessment of the body of available knowledge. A single clinical trial, even a large one, is seldom sufficient to provide a confident answer to a clinical question. Indeed, one analysis suggested that most research claims are ultimately proven to be incorrect or inaccurate when additional studies have been performed [1]. At the same time, it is well-established that large randomized controlled trials do not always confirm the results of prior meta-analyses [2-4]. The "truth" needs to be understood by examining all sources of data as critically and objectively as possible.

There are several potential benefits to performing systematic analysis, which may also include meta-analysis:

Unique aspects to a single randomized trial, involving the participating patient population, the protocol, the setting in which the trial is performed, or the expertise of the involved clinicians, may limit its generalizable to other settings or individual patients. The conclusions of systematic reviews may be more generalizable than single studies.

Combining studies in meta-analyses increases the sample size and generally produces more precise estimates of the effect size (ie, estimates that have smaller confidence intervals) than a single randomized trial.

Clinicians rarely have the time or resources to critically evaluate the body of evidence relevant to a particular clinical question, and a systematic review can facilitate this investigation.

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Literature review current through: Nov 2017. | This topic last updated: Jul 12, 2016.
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