Ethical implications of excessive cluster sizes in cluster randomised trials

BMJ Quality & Safety
Karla HemmingCharles Weijer

Abstract

The cluster randomised trial (CRT) is commonly used in healthcare research. It is the gold-standard study design for evaluating healthcare policy interventions. A key characteristic of this design is that as more participants are included, in a fixed number of clusters, the increase in achievable power will level off. CRTs with cluster sizes that exceed the point of levelling-off will have excessive numbers of participants, even if they do not achieve nominal levels of power. Excessively large cluster sizes may have ethical implications due to exposing trial participants unnecessarily to the burdens of both participating in the trial and the potential risks of harm associated with the intervention. We explore these issues through the use of two case studies. Where data are routinely collected, available at minimum cost and the intervention poses low risk, the ethical implications of excessively large cluster sizes are likely to be low (case study 1). However, to maximise the social benefit of the study, identification of excessive cluster sizes can allow for prespecified and fully powered secondary analyses. In the second case study, while there is no burden through trial participation (because the outcome data are routinely co...Continue Reading

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May 11, 2013·BMJ : British Medical Journal·Monica TaljaardUNKNOWN Ottawa Ethics of Cluster Randomised Trials Consensus Group
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Apr 11, 2017·Clinical Trials : Journal of the Society for Clinical Trials·Monica TaljaardCharles Weijer
Jul 16, 2017·BMJ : British Medical Journal·K HemmingM Taljaard

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