Skip to content

Advertisement

  • Poster presentation
  • Open Access

Stepped-wedge cluster randomised controlled trials: some variations on the common design

  • 1 and
  • 1
Trials201314 (Suppl 1) :P15

https://doi.org/10.1186/1745-6215-14-S1-P15

  • Published:

Keywords

  • Public Health
  • Health Service
  • Treatment Effect
  • Linear Mixed Model
  • Service Evaluation

Stepped wedge cluster randomised trials (SW-CRTs) are being used with increasing frequency in health service evaluation. Conventionally, these studies are designed with equally spaced steps, with an equal number of clusters randomised at each step, and data collected at each and every step.

Here we introduce several variations on this design and consider implications for power. One modifiction we consider is where the number of clusters varies at each step, or where at some steps data are not collected. We show that the parallel CRT with staggered, but balanced randomisation, can be considered a special case of the incomplete SW-CRT. And, we extend these designs to allow for multiple layers of clustering, for example wards within a hospital. Building on results for complete designs, power and detectable difference are derived using Wald-test and obtaining the variance-covariance matrix of the treatment effect assuming a generalised linear mixed model. These variations are illustrated by several real examples.

Authors’ Affiliations

(1)
University of Birmingham, Birmingham, UK

Copyright

© Hemming and Girling; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Please note that comments may be removed without notice if they are flagged by another user or do not comply with our community guidelines.

Advertisement