Projects per year
Abstract
In cluster-randomized trials, sometimes the effect of the intervention being studied differs between clusters, commonly referred to as treatment effect heterogeneity. In the analysis of stepped wedge and cluster-randomized crossover trials, it is possible to include terms in outcome regression models to allow for such treatment effect heterogeneity yet this is not frequently considered. Outside of some simulation studies of specific cases where the outcome is binary, the impact of failing to include terms for treatment effect heterogeneity on the variance of the treatment effect estimator is unknown. We analytically examine the impact of failing to include terms for treatment effect heterogeneity on the variance of the treatment effect estimator, when outcomes are continuous. Using analysis of variance and feasible generalized least squares we provide expressions for this variance. For both the cluster-randomized crossover design and the stepped wedge design, our analytic derivations indicate that failing to include treatment effect heterogeneity results in the estimates for variance of the treatment effect that are too small, leading to inflation of type I error rates. We therefore recommend assessing the sensitivity of sample size calculations and conclusions drawn from the analysis of cluster randomized trials to the inclusion of treatment effect heterogeneity.
Original language | English |
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Pages (from-to) | 2503-2525 |
Number of pages | 23 |
Journal | Statistical Methods in Medical Research |
Volume | 30 |
Issue number | 11 |
DOIs | |
Publication status | Published - Nov 2021 |
Keywords
- Cluster randomized crossover
- generalized least squares
- linear mixed models
- misspecification
- stepped wedge
- treatment effect heterogeneity
Projects
- 1 Finished
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Pragmatic cluster randomised trials: Bridging the gap between theory and practice
Forbes, A. (Primary Chief Investigator (PCI)), Hemming, K. (Chief Investigator (CI)) & Taljaard, M. (Chief Investigator (CI))
National Health and Medical Research Council (NHMRC) (Australia)
1/01/20 → 31/12/22
Project: Research