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Ethical issues posed by cluster randomized trials in health research

Charles Weijer123*, Jeremy M Grimshaw45, Monica Taljaard46, Ariella Binik1, Robert Boruch7, Jamie C Brehaut46, Allan Donner38, Martin P Eccles9, Antonio Gallo110, Andrew D McRae1113, Raphael Saginur12 and Merrick Zwarenstein13

Author Affiliations

1 Rotman Institute of Philosophy, Department of Philosophy, University of Western Ontario, London, ON, N6A 5B8, Canada

2 Department of Medicine, University of Western Ontario, 339 Windermere Road, London, ON, N6A 5A5, Canada

3 Department of Epidemiology and Biostatistics, University of Western Ontario, London, ON, N6A 5C1, Canada

4 Ottawa Hospital Research Institute, Clinical Epidemiology Program, Civic Campus, 1053 Carling Avenue, Ottawa, ON, K1Y 4E9, Canada

5 Department of Medicine, Faculty of Medicine, University of Ottawa, ON, K1H 8L6, Canada

6 Department of Epidemiology and Community Medicine, University of Ottawa, ON, K1H 8M5, Canada

7 Graduate School of Education and Statistics Department, Wharton School, University of Pennsylvania, 3700 Walnut Street, Philadelphia, PA, 19104, USA

8 Robarts Clinical Trials, Robarts Research Institute, London, ON, N6A 5K8, Canada

9 Institute of Health and Society, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK

10 Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, N6A 5C1, Canada

11 Division of Emergency Medicine, University of Calgary, Foothills Medical Centre, 1403 29th Street NW, Calgary, AB, T2N 2T9, Canada

12 Department of Medicine, University of Ottawa and Ottawa Hospital, Ottawa Hospital Research Institute, 1053 Carling Avenue, Ottawa, ON, K1Y 4E9, Canada

13 Centre for Health Services Sciences, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto ON, M4N 3M5, Canada

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Trials 2011, 12:100  doi:10.1186/1745-6215-12-100

Published: 20 April 2011


The cluster randomized trial (CRT) is used increasingly in knowledge translation research, quality improvement research, community based intervention studies, public health research, and research in developing countries. However, cluster trials raise difficult ethical issues that challenge researchers, research ethics committees, regulators, and sponsors as they seek to fulfill responsibly their respective roles. Our project will provide a systematic analysis of the ethics of cluster trials. Here we have outlined a series of six areas of inquiry that must be addressed if the cluster trial is to be set on a firm ethical foundation:

1. Who is a research subject?

2. From whom, how, and when must informed consent be obtained?

3. Does clinical equipoise apply to CRTs?

4. How do we determine if the benefits outweigh the risks of CRTs?

5. How ought vulnerable groups be protected in CRTs?

6. Who are gatekeepers and what are their responsibilities?

Subsequent papers in this series will address each of these areas, clarifying the ethical issues at stake and, where possible, arguing for a preferred solution. Our hope is that these papers will serve as the basis for the creation of international ethical guidelines for the design and conduct of cluster randomized trials.