Using metaanalysis to evaluate evidence: practical tips and traps.

Although practising evidence-based medicine is the goal of most physicians, it can be a real challenge to sift through the vast body of data to determine the best strategies. Most clinical guidelines regard replicated randomized controlled trials (RCTs), metaanalyses, and systematic reviews as the highest level of evidence to support treatment recommendations. High-quality metaanalyses can overcome many of the drawbacks of individual RCTs and qualitative reviews. They can reduce bias, provide adequate power to demonstrate real differences in outcomes, and resolve the results of inconsistent studies. This paper focuses on basic principles and terms used in metaanalysis, so that clinicians can appropriately evaluate and use their results to guide treatment decisions.