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

Gordon H. Guyatt, Andrew D. Oxman, Victor Montori, Gunn Vist, Regina Kunz, Jan Brozek, Pablo Alonso-Coello, Ben Djulbegovic, David Atkins, Yngve Falck-Ytter, John W. Williams, Joerg Meerpohl, Susan L. Norris, Elie A. Akl, Holger J. Schünemann

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)1277-1282
Number of pages6
JournalJournal of Clinical Epidemiology
Issue number12
StatePublished - Dec 2011


  • Conflict of interest
  • Funnel plot
  • Pharmaceutical industry
  • Publication bias
  • Quality of evidence

ASJC Scopus subject areas

  • Epidemiology


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