• Alexandra Nolting, Matthias Perleth, Gero Langer, Joerg J Meerpohl, Gerald Gartlehner, Angela Kaminski-Hartenthaler, and Holger J Schünemann.
• Abteilung Fachberatung Medizin, Gemeinsamer Bundesausschuss, Berlin, Germany. alexandra.nolting@g-ba.de
• Z Evid Fortbild Qual Gesundhwes. 2012 Jan 1; 106 (9): 670-6.

AbstractIn 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.Copyright © 2012. Published by Elsevier GmbH.

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