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Inadequate reporting of research ethics review and informed consent in cluster randomised trials: review of random sample of published trials

BMJ 2011; 342 doi: (Published 11 May 2011) Cite this as: BMJ 2011;342:d2496
  1. Monica Taljaard, scientist1,
  2. Andrew D McRae, research director2,
  3. Charles Weijer, professor3,
  4. Carol Bennett, research coordinator1,
  5. Stephanie Dixon, postdoctoral fellow4,
  6. Julia Taleban, PhD candidate4,
  7. Zoe Skea, research fellow5,
  8. Martin P Eccles, professor6,
  9. Jamie C Brehaut, scientist1,
  10. Allan Donner, professor4,
  11. Raphael Saginur, professor7,
  12. Robert F Boruch, professor8,
  13. Jeremy M Grimshaw, senior scientist1
  1. 1Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa Hospital, Civic Campus, 1053 Carling Avenue, Ottawa, ON, Canada K1Y 4E9
  2. 2Division of Emergency Medicine, University of Calgary, Foothills Medical Centre, Calgary, AB, Canada
  3. 3Philosophy and Medicine, Rotman Institute of Philosophy, Department of Philosophy, University of Western Ontario, London, ON, Canada
  4. 4Department of Epidemiology and Biostatistics, Schulich School of Medicine and Density, University of Western Ontario, London, ON, Canada
  5. 5Health Services Research Unit, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
  6. 6Clinical Effectiveness, Institute of Health and Society, Newcastle University, Newcastle upon Tyne NE2 4AX, UK
  7. 7Medicine, Ottawa Hospital, Ottawa ON, Canada
  8. 8Education and Statistics, Graduate School of Education, University of Pennsylvania, Philadelphia, PA 19104, USA
  1. Correspondence to: M Taljaard mtaljaard{at}
  • Accepted 8 March 2011


Objectives To investigate the extent to which authors of cluster randomised trials adhered to two basic requirements of the World Medical Association’s Declaration of Helsinki and the International Committee of Medical Journal Editors’ uniform requirements for manuscripts (namely, reporting of research ethics review and informed consent), to determine whether the adequacy of reporting has improved over time, and to identify characteristics of cluster randomised trials associated with reporting of ethics practices.

Design Review of a random sample of published cluster randomised trials from an electronic search in Medline.

Setting Cluster randomised trials in health research published in English language journals from 2000 to 2008.

Study sample 300 cluster randomised trials published in 150 journals.

Results 77 (26%, 95% confidence interval 21% to 31%) trials failed to report ethics review. The proportion reporting ethics review increased significantly over time (P<0.001). Trials with data collection interventions at the individual level were more likely to report ethics review than were trials that used routine data sources only (79% (n=151) v 55% (23); P=0.008). Trials that accounted for clustering in the design and analysis were more likely to report ethics review. The median impact factor of the journal of publication was higher for trials that reported ethics review (3.4 v 2.3; P<0.001). 93 (31%, 26% to 36%) trials failed to report consent. Reporting of consent increased significantly over time (P<0.001). Trials with interventions targeting participants at the individual level were more likely to report consent than were trials with interventions targeting the cluster level (87% (90) v 48% (41); P<0.001). Trials with data collection interventions at the individual level were more likely to report consent than were those that used routine data sources only (78% (146) v 29% (11); P<0.001).

Conclusions Reporting of research ethics protections in cluster randomised trials is inadequate. In addition to research ethics approval, authors should report whether informed consent was sought, from whom consent was sought, and what consent was for.


  • Contributors: MT, CW, JMG, JCB, MPE, AD, RS, ADMcR, and RFB contributed to the conception and design of the study. MT, ADMcR, CB, SD, JT, and ZS abstracted the data. MT drafted the article and analysed the data. All authors contributed to the interpretation of the data, commented on the first draft and revised the article critically for important intellectual content, and approved the final version. All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. MT is the guarantor.

  • Funding: This study has been funded by operating grants MOP85066 and MOP89790 from the Canadian Institutes of Health Research. The funding agency had no role in the study design; collection, analysis, or interpretation of data; writing of the manuscript; or the decision to submit the manuscript for publication.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethics approval: This study was not approved by a research ethics committee, nor did we request informed consent from the authors of the articles included in our review, because our study did not meet the criteria for human subjects research.

  • ADMcR holds a fellowship award from the Canadian Institutes of Health Research. JMG and CW both hold Canada Research chairs.

  • Data sharing: Technical appendix, statistical code, and dataset available from the corresponding author at mtaljaard{at}

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