Subgroup analyses in randomised controlled trials: cohort study on trial protocols and journal publications

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DISCO Study Grp , Kasenda , B , Schandelmaier , S , Sun , X , Tikkinen , K & Briel , M 2014 , ' Subgroup analyses in randomised controlled trials: cohort study on trial protocols and journal publications ' , BMJ : British Medical Journal , vol. 349 , g4539 . https://doi.org/10.1136/bmj.g4539

Title: Subgroup analyses in randomised controlled trials: cohort study on trial protocols and journal publications
Author: DISCO Study Grp; Kasenda, Benjamin; Schandelmaier, Stefan; Sun, Xin; Tikkinen, Kari; Briel, Matthias
Contributor: University of Helsinki, Urologian yksikkö
Date: 2014
Language: eng
Number of pages: 11
Belongs to series: BMJ : British Medical Journal
ISSN: 0959-535X
URI: http://hdl.handle.net/10138/304999
Abstract: OBJECTIVE: To investigate the planning of subgroup analyses in protocols of randomised controlled trials and the agreement with corresponding full journal publications. DESIGN: Cohort of protocols of randomised controlled trial and subsequent full journal publications. SETTING: Six research ethics committees in Switzerland, Germany, and Canada. DATA SOURCES: 894 protocols of randomised controlled trial involving patients approved by participating research ethics committees between 2000 and 2003 and 515 subsequent full journal publications. RESULTS: Of 894 protocols of randomised controlled trials, 252 (28.2%) included one or more planned subgroup analyses. Of those, 17 (6.7%) provided a clear hypothesis for at least one subgroup analysis, 10 (4.0%) anticipated the direction of a subgroup effect, and 87 (34.5%) planned a statistical test for interaction. Industry sponsored trials more often planned subgroup analyses compared with investigator sponsored trials (195/551 (35.4%) v 57/343 (16.6%), P<0.001). Of 515 identified journal publications, 246 (47.8%) reported at least one subgroup analysis. In 81 (32.9%) of the 246 publications reporting subgroup analyses, authors stated that subgroup analyses were prespecified, but this was not supported by 28 (34.6%) corresponding protocols. In 86 publications, authors claimed a subgroup effect, but only 36 (41.9%) corresponding protocols reported a planned subgroup analysis. CONCLUSIONS: Subgroup analyses are insufficiently described in the protocols of randomised controlled trials submitted to research ethics committees, and investigators rarely specify the anticipated direction of subgroup effects. More than one third of statements in publications of randomised controlled trials about subgroup prespecification had no documentation in the corresponding protocols. Definitive judgments regarding credibility of claimed subgroup effects are not possible without access to protocols and analysis plans of randomised controlled trials.
Subject: 3142 Public health care science, environmental and occupational health
trial protocols
Randomised controlled trials
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