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

• Published in: Journal of clinical epidemiology 2011-12, Vol.64 (12), p.1277-1282
• Main Authors: Guyatt, Gordon H, Oxman, Andrew D, Montori, Victor, Vist, Gunn, Kunz, Regina, Brozek, Jan, Alonso-Coello, Pablo, Djulbegovic, Ben, Atkins, David, Falck-Ytter, Yngve, Williams, John W, Meerpohl, Joerg, Norris, Susan L, Akl, Elie A, Schünemann, Holger J
• Format: Article
• Language: English
• Subjects: Clinical trials; Conflict of interest; Cross-Sectional Studies; Drug Industry; Epidemiology; Estimates; Evidence-Based Medicine - standards; Funnel plot; GRADE; Grey literature; Internal Medicine; Meta-Analysis as Topic; Observational studies; Peer review; Pharmaceutical industry; Practice Guidelines as Topic; Publication Bias; Quality of evidence; Randomized Controlled Trials as Topic - standards; Review Literature as Topic; Statistics as Topic; Systematic review
• ISSN: 0895-4356; 1878-5921
• DOI: 10.1016/j.jclinepi.2011.01.011

Abstract 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.