Statistically significant meta-analyses of clinical trials have modest credibility and inflated effects

dc.contributor.authorPereira, T. V.en
dc.contributor.authorIoannidis, J. P.en
dc.date.accessioned2015-11-24T18:50:35Z
dc.date.available2015-11-24T18:50:35Z
dc.identifier.issn1878-5921-
dc.identifier.urihttps://olympias.lib.uoi.gr/jspui/handle/123456789/18108
dc.rightsDefault Licence-
dc.subjectBias (Epidemiology)en
dc.subjectClinical Trials as Topic/*standardsen
dc.subjectHealth Services Research/methods/standardsen
dc.subjectHumansen
dc.subject*Meta-Analysis as Topicen
dc.titleStatistically significant meta-analyses of clinical trials have modest credibility and inflated effectsen
heal.abstractOBJECTIVE: To assess whether nominally statistically significant effects in meta-analyses of clinical trials are true and whether their magnitude is inflated. STUDY DESIGN AND SETTING: Data from the Cochrane Database of Systematic Reviews 2005 (issue 4) and 2010 (issue 1) were used. We considered meta-analyses with binary outcomes and four or more trials in 2005 with P<0.05 for the random-effects odds ratio (OR). We examined whether any of these meta-analyses had updated counterparts in 2010. We estimated the credibility (true-positive probability) under different prior assumptions and inflation in OR estimates in 2005. RESULTS: Four hundred sixty-one meta-analyses in 2005 were eligible, and 80 had additional trials included by 2010. The effect sizes (ORs) were smaller in the updating data (2005-2010) than in the respective meta-analyses in 2005 (median 0.85-fold, interquartile range [IQR]: 0.66-1.06), even more prominently for meta-analyses with less than 300 events in 2005 (median 0.67-fold, IQR: 0.54-0.96). Mean credibility of the 461 meta-analyses in 2005 was 63-84% depending on the assumptions made. Credibility estimates changed >20% in 19-31 (24-39%) of the 80 updated meta-analyses. CONCLUSIONS: Most meta-analyses with nominally significant results pertain to truly nonnull effects, but exceptions are not uncommon. The magnitude of observed effects, especially in meta-analyses with limited evidence, is often inflated.en
heal.accesscampus-
heal.fullTextAvailabilityTRUE-
heal.identifier.primary10.1016/j.jclinepi.2010.12.012-
heal.identifier.secondaryhttp://www.ncbi.nlm.nih.gov/pubmed/21454050-
heal.identifier.secondaryhttp://ac.els-cdn.com/S0895435611000096/1-s2.0-S0895435611000096-main.pdf?_tid=850ed0e83aa218ff99419c07f5ba70ba&acdnat=1333363381_46c982d4ce43cdc44491c0772f59f1d7-
heal.journalNameJ Clin Epidemiolen
heal.journalTypepeer-reviewed-
heal.languageen-
heal.publicationDate2011-
heal.recordProviderΠανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών Υγείας. Τμήμα Ιατρικήςel
heal.typejournalArticle-
heal.type.elΆρθρο Περιοδικούel
heal.type.enJournal articleen

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