Cluster-randomized trials: A closer look

Background: The cluster-randomized trial is the methodology of choice for evaluating interventions administered at the group level such as public health and healthcare quality improvement interventions. Because of unique features of this design, it can be difficult to apply standard research ethics guidelines to cluster-randomized trials. The Ottawa Statement on the Ethical Design and Conduct of Cluster-Randomized Trials provides researchers and research ethics committees with comprehensive guidance on the ethical design, conduct and review of cluster-randomized trials. The Ottawa Statement supplements current national and international research ethics guidelines with guidance that is specific to cluster-randomized trials. In a recently published commentary, three examples drawn from the ClinicalTrials.gov registry were used to illustrate challenges associated with the cluster-randomized trial design. The commentary argued that the Ottawa Statement fails to provide comprehensive ethical guidance. In this article, we illustrate the application of the Ottawa Statement to the three trials. We challenge the conclusions reached in the commentary by demonstrating that an ethical analysis requires complete information. We correct some misperceptions about the cluster-randomized trial design. Methods: We collected essential additional information by contacting the authors of trials and by referring to published trial articles. We used the Ottawa Statement to conduct an ethical analysis of each trial and to address a number of substantive concerns raised regarding the identification of study participants, informed consent and harm benefit analysis. Results: In the two cases in which we were able to obtain detailed study information, we were able to complete the ethical analysis prescribed by the Ottawa Statement. Conclusion: The Ottawa Statement does provide a useful framework for the ethical design, review and conduct of cluster-randomized trials.