GRADE guidelines: 5. Rating the quality of evidence--publication bias

J Clin Epidemiol. 2011 Dec;64(12):1277-82. doi: 10.1016/j.jclinepi.2011.01.011. Epub 2011 Jul 30.


In the GRADE approach, randomized trials start as high-quality evidence and observational studies as low-quality evidence, but both can be rated down if a body of evidence is associated with a high risk of publication bias. Even when individual studies included in best-evidence summaries have a low risk of bias, publication bias can result in substantial overestimates of effect. Authors should suspect publication bias when available evidence comes from a number of small studies, most of which have been commercially funded. A number of approaches based on examination of the pattern of data are available to help assess publication bias. The most popular of these is the funnel plot; all, however, have substantial limitations. Publication bias is likely frequent, and caution in the face of early results, particularly with small sample size and number of events, is warranted.

MeSH terms

  • Cross-Sectional Studies
  • Drug Industry*
  • Evidence-Based Medicine / standards*
  • Meta-Analysis as Topic
  • Practice Guidelines as Topic*
  • Publication Bias*
  • Randomized Controlled Trials as Topic / standards*
  • Review Literature as Topic
  • Statistics as Topic