title: [GRADE guidelines: 5. Rating the quality of evidence: publication bias].
abstract: In the GRADE approach, randomized trials are classified 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.
authors.affiliation: Abteilung Fachberatung Medizin, Gemeinsamer Bundesausschuss, Berlin, Germany. alexandra.nolting@g-ba.de
authors.forename: Alexandra
authors.initials: A
authors.lastname: Nolting
authors.forename: Matthias
authors.initials: M
authors.lastname: Perleth
authors.forename: Gero
authors.initials: G
authors.lastname: Langer
authors.forename: Joerg J
authors.initials: JJ
authors.lastname: Meerpohl
authors.forename: Gerald
authors.initials: G
authors.lastname: Gartlehner
authors.forename: Angela
authors.initials: A
authors.lastname: Kaminski-Hartenthaler
authors.forename: Holger J
authors.initials: HJ
authors.lastname: Schünemann
mesh_terms: D003627:Data Interpretation, Statistical; D019317:Evidence-Based Medicine / Q000592:standards*; D005858:Germany; D006801:Humans; D017594:Publication Bias / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic / Q000145:classification* / Q000592:standards*; D012107:Research Design; D012109:Research Support as Topic; D012196:Review Literature as Topic; D018401:Sample Size