Agnes Dechartres1, Ignacio Atal2, Carolina Riveros3, Joerg Meerpohl4, Philippe Ravaud5. 1. INSERM U1153, Université Paris Descartes, Sorbonne Paris Cité, Hôpital Hôtel Dieu, Assistance Publique-Hôpitaux de Paris, Cochrane France, and Sorbonne Université, Institut Pierre Louis de Santé Publique, Hôpitaux Universitaires Pitié Salpêtrière - Charles Foix, Assistance Publique-Hôpitaux de Paris, Paris, France (A.D.). 2. INSERM U1153 and Cochrane France, Paris, France (I.A.). 3. INSERM U1153 and Hôpital Hôtel Dieu, Assistance Publique-Hôpitaux de Paris, Paris, France (C.R.). 4. Hôpital Hôtel Dieu, Assistance Publique-Hôpitaux de Paris and Cochrane France, Paris, France, and Institute for Evidence in Medicine (for Cochrane Germany Foundation), University of Freiburg Medical Center, Freiburg, Germany (J.M.). 5. INSERM U1153, Université Paris Descartes, Sorbonne Paris Cité, Hôpital Hôtel Dieu, Assistance Publique-Hôpitaux de Paris, and Cochrane France, Paris, France, and Columbia University Mailman School of Public Health, New York, New York (P.R.).
Abstract
Background: Evidence about the effect on meta-analysis results of including unpublished trials or those published in languages other than English is unclear or discordant. Purpose: To compare treatment effects between published and unpublished randomized controlled trials (RCTs) and between trials published in English and other languages using a meta-epidemiologic approach. Data Sources: Cochrane reviews published between March 2011 and January 2017 and trial references cited in the reviews. Study Selection: RCTs included in meta-analyses of 3 or more trials with a binary efficacy outcome. Data Extraction: Trial characteristics were extracted by original review authors. A single reviewer assessed publication status and language, with quality assurance by another investigator. Data Synthesis: Among 5659 RCTs included in 698 meta-analyses, 5303 (93.7%) were published in journal articles and 356 (6.3%) were unpublished. Of journal articles, 92.6% (4910 of 5303) were published in English and 7.4% (393 of 5303) in another language. Treatment effects were larger in published than unpublished trials (combined ratio of odds ratios [ROR] for 174 meta-analyses, 0.90 [95% CI, 0.82 to 0.98]; I2 = 19.3%; τ2 = 0.0492). Treatment effects were also larger for trials published in a language other than English than in English (combined ROR for 147 meta-analyses, 0.86 [CI, 0.78 to 0.95]; I2 = 0%; τ2 = 0.0000). Limitation: Reliance on the primary reference cited by review authors as the record of interest. Conclusion: In meta-analyses, treatment effects were larger in published than unpublished trials and, for published trials, in those published in a language other than English than in English. Primary Funding Source: Cochrane France.
Background: Evidence about the effect on meta-analysis results of including unpublished trials or those published in languages other than English is unclear or discordant. Purpose: To compare treatment effects between published and unpublished randomized controlled trials (RCTs) and between trials published in English and other languages using a meta-epidemiologic approach. Data Sources: Cochrane reviews published between March 2011 and January 2017 and trial references cited in the reviews. Study Selection: RCTs included in meta-analyses of 3 or more trials with a binary efficacy outcome. Data Extraction: Trial characteristics were extracted by original review authors. A single reviewer assessed publication status and language, with quality assurance by another investigator. Data Synthesis: Among 5659 RCTs included in 698 meta-analyses, 5303 (93.7%) were published in journal articles and 356 (6.3%) were unpublished. Of journal articles, 92.6% (4910 of 5303) were published in English and 7.4% (393 of 5303) in another language. Treatment effects were larger in published than unpublished trials (combined ratio of odds ratios [ROR] for 174 meta-analyses, 0.90 [95% CI, 0.82 to 0.98]; I2 = 19.3%; τ2 = 0.0492). Treatment effects were also larger for trials published in a language other than English than in English (combined ROR for 147 meta-analyses, 0.86 [CI, 0.78 to 0.95]; I2 = 0%; τ2 = 0.0000). Limitation: Reliance on the primary reference cited by review authors as the record of interest. Conclusion: In meta-analyses, treatment effects were larger in published than unpublished trials and, for published trials, in those published in a language other than English than in English. Primary Funding Source: Cochrane France.