Publication bias: a brief review for clinicians.

Systematic reviews and meta-analyses provide the highest level of evidence to guide clinical decisions and inform practice guidelines. Publication bias results from the selective publication of studies based on the direction and magnitude of their results--studies without statistical significance (negative studies) are less likely to be published. Bias results from pooling the results from published studies alone leading to overestimation of the effectiveness of the intervention. In this review we define publication bias, how it affects the results of systematic reviews, how it can be detected and minimized, and how it can be prevented.