Cluster Trials 2012

The CONSORT extension for cluster trials was recently updated to be in-line with the CONSORT 2010 Statement and published in the British Medical Journal September 2012.  You can freely access the updated article and checklist on this page or the journal website.

The main CONSORT Statement provides recommendations for reporting parallel group randomized trials, in which individual participants are randomly assigned to health care interventions. Cluster trials, however, randomize interventions to groups of patients (e.g., families, medical practices) rather than to individual patients.

The main problem associated with their design, conduct, analysis, and interpretation, compared with individually randomized trials, is that two different units of measurement—the cluster and the patient—are used. Each needs to be reported carefully.

An extension to the CONSORT Statement for cluster randomized trials was developed in which recommendations for the reporting of these trials are presented. The paper discusses the methodology and gives an explanation of each suggested modification to the main CONSORT checklist.


Campbell MK, Piaggio G, Elbourne DR, Altman DG; for the CONSORT Group. Consort 2010 statement: extension to cluster randomised trials. BMJ. 2012 Sep 4;345:e5661. Full text PDF. PMID: 22951546

Visit the CONSORT database for additional literature on cluster trials.

Page last edited: 19 February 2013