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. 2024 Feb;72(1):202196.
doi: 10.1016/j.jeph.2024.202196. Epub 2024 Feb 10.

How should a cluster randomized trial be analyzed?

Laurent Billot  1 , Andrew Copas  2 , Clemence Leyrat  3 , Andrew Forbes  4 , Elizabeth L Turner  5
Affiliations

How should a cluster randomized trial be analyzed?

Laurent Billot et al. J Epidemiol Popul Health. 2024 Feb.

Abstract

In cluster randomized trials, individuals from the same cluster tend to have more similar outcomes than individuals from different clusters. This correlation must be taken into account in the analysis of every cluster trial to avoid incorrect inferences. In this paper, we describe the principles guiding the analysis of cluster trials including how to correctly account for intra-cluster correlations as well as how to analyze more advanced designs such as stepped-wedge and cluster cross-over trials. We then describe how to handle specific issues such as small sample sizes and missing data.

Keywords: Analysis; Cluster crossover trials; Cluster randomized trials; Stepped-wedge trials.

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Conflict of interest statement

Declaration of competing interest The authors declare there is no conflict of interests.

Figures

Fig. 1
Fig. 1. Example of stepped-wedge trial with 4 sequences (5 periods).
In a stepped-wedge trial, more clusters are receiving the intervention in later periods, necessitating appropriate adjustment for time to avoid potential confounding biases.
See this image and copyright information in PMC

References

    1. Eldridge S, Kerry S. A practical guide to cluster randomised trials in health services research. Statistics in practice. 2012:298.
    1. Leyrat C, Eldridge S, Taljaard M, Hemming K. Practical considerations for sample size calculation for cluster randomized trials. J Epidemiol Popul Health. 2024;72(1):202198. - PubMed
    1. Giraudeau B, Weijer C, Eldridge SM, Hemming K, Taljaard M. Why and when should we cluster randomize? J Epidemiol Popul Health. 2024;72(1):202197. - PubMed
    1. Hemming K, Copas A, Forbes A, Kasza J. What type of cluster randomized trial for which setting? J Epidemiol Popul Health. 2024;72(1):202195. - PubMed
    1. Hayes RJ, Moulton LH. Cluster randomised trials. CRC Press; Boca Raton: 2017. p. 424.

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