A review of the use of covariates in cluster randomized trials uncovers marked discrepancies between guidance and practice

Wright, Neil, Ivers, Noah, Eldridge, Sandra, Taljaard, Monica and Bremner, Stephen (2014) A review of the use of covariates in cluster randomized trials uncovers marked discrepancies between guidance and practice. Journal of Clinical Epidemiology, 68 (6). pp. 603-609. ISSN 0895-4356

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Abstract

Objectives: Reviews of the handling of covariates in trials have explicitly excluded cluster randomized trials (CRTs). In this study, we review the use of covariates in randomization, the reporting of covariates, and adjusted analyses in CRTs. Study Design and Setting: We reviewed a random sample of 300 CRTs published between 2000 and 2008 across 150 English language journals. Results: Fifty-eight percent of trials used covariates in randomization. Only 69 (23%) included tables of cluster- and individual-level covariates. Fifty-eight percent reported significance tests of baseline balance. Of 207 trials that reported baseline measures of the primary outcome, 155 (75%) subsequently adjusted for these in analyses. Of 174 trials that used covariates in randomization, 30 (17%) included an analysis adjusting for all those covariates. Of 219 trial reports that included an adjusted analysis of the primary outcome, only 71 (32%) reported that covariates were chosen a priori. Conclusion: There are some marked discrepancies between practice and guidance on the use of covariates in the design, analysis, and reporting of CRTs. It is essential that researchers follow guidelines on the use and reporting of covariates in CRTs, promoting the validity of trial conclusions and quality of trial reports.

Item Type: Article
Keywords: Cluster randomized trials; Covariates; Restricted randomization, consort statement, adjusted analyses, baseline imbalance
Schools and Departments: Brighton and Sussex Medical School > Brighton and Sussex Medical School
Brighton and Sussex Medical School > Primary Care and Public Health
Depositing User: Jane Hale
Date Deposited: 30 Jun 2015 09:46
Last Modified: 16 Mar 2017 17:37
URI: http://sro.sussex.ac.uk/id/eprint/55019

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Project NameSussex Project NumberFunderFunder Ref
N.I. is supported by fellowship awardsUnsetCanadian Institutes of Health Research and the Department of Family and Community Medicine at the University of TorontoUnset
N.W.’s PhD researchUnsetMedical Research CouncilUnset