Elsevier

Mayo Clinic Proceedings

Volume 75, Issue 12, December 2000, Pages 1284-1288
Mayo Clinic Proceedings

Review
Publication Bias: A Brief Review for Clinicians

https://doi.org/10.4065/75.12.1284Get rights and content

Systematic reviews and mata-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.

Section snippets

PUBLICATION BIAS

A systematic review follows a protocol describing the scope of the question, criteria for inclusion and exclusion of primary studies, a search strategy, data extraction, quality assessment procedures, and data analysis. Bias can intrude at any of these steps. Perhaps the most difficult form of bias for reviewers to overcome is publication bias, which influences the selection of studies for inclusion in the review. Publication bias follows from the selective publication of manuscripts based on

DETECTING PUBLICATION BIAS

Since even comprehensive efforts may fail to identify all unpublished studies, reviewers may conduct procedures designed to determine the likelihood that publication bias is influencing their results. These methods may be graphical (the funnel plot and the trim-and-fill method) or analytical (fail-safe N, sensitivity analysis, and prospective registry).

An estimated treatment effect is more precise (has a narrower confidence interval) in a study with a larger number of patient events compared

PREVENTING PUBLICATION BIAS

Prospective study registration with accessible results is likely to represent the best solution. Proposals exist to link prospective registration to the work of institutional review boards or ethics review boards40 or to the editorial process of medical journals and publishing societies.41 Some pharmaceutical companies have made their research information available online.42 Some journals, like The Lancet, have established Web sites for posting study protocols and reports of completed studies

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    Dr Smieja is a research fellow of the Heart and Stroke Foundation of Canada. This work was supported in part by the American Medical Association.

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