Resources for researchers

stepped wedge of the day cartoon

When following links to journal articles in the sections below, note that some journals will require an institutional login or subscription.

Go straight to:

or scroll down for more.

Reporting guidelines

The CONSORT guidance on how to report findings from stepped wedge trials can be found here:

  • Hemming K, Taljaard M, McKenzie JE, et al. Reporting of stepped wedge cluster randomised trials: extension of the CONSORT 2010 statement with explanation and elaboration. BMJ 2018;363:k1614.

Reflective articles

Here are some more reflective articles on stepped wedge trials from academic journals:

And here is a helpful YouTube video on cluster randomised and stepped wedge trials by Sandra Eldridge:

Analysis

For a comprehensive discussion of mixed effects models for the analysis of stepped wedge trials:

For permutation tests and approaches with less reliance on modelling assumptions:

  • Thompson JA, Davey C, Fielding K, et al. Robust analysis of stepped wedge trials using cluster-level summaries within periods. Stat Med 2018;37:2487-500.
  • Thompson J, Davey C, Hayes R, et al. Permutation tests for stepped-wedge cluster-randomized trials. Stata J 2019;19:803-819.
  • Kennedy-Staffer L, de Gruttola V, Lipsitch M. Novel methods for the analysis of stepped wedge cluster randomised trials. Stat Med 2020;39:815-844.

Sample size calculation

Software packages and apps for sample size calculation for stepped wedge trials:

  • The Shiny CRT Calculator: R Shiny app for calculating power and sample size for cluster randomised trials (including stepped wedge).
  • swdpr: SAS macro and R package for calculating power for stepped wedge trials with continuous or binary outcomes.
  • SWSamp: R package for calculating sample size for stepped wedge trials by simulation.
  • swCRTdesign: R Shiny app for calculating power for stepped wedge designs.

And some useful journal articles on sample size calculation, for background:

  • Hooper R, Bourke L. Cluster randomised trials with repeated cross sections: alternatives to parallel group designs. BMJ 2015;350:h2925.
  • Hooper R, Teerenstra S, de Hoop E, Eldridge S. Sample size calculation for stepped wedge and other longitudinal cluster randomised trials. Stat Med 2016;35:4718-4728.
  • Girling AJ. Relative efficiency of unequal cluster sizes in stepped wedge and other trial designs under longitudinal or cross‐sectional sampling. Stat Med 2018;37:4652-4664.
  • Li F, Turner EL, Preisser JS. Sample size determination for GEE analyses of stepped wedge cluster randomized trials. Biometrics 2018;74:1450-1458.
  • Teerenstra, Taljaard, Haenen, et al. Sample size calculation for stepped-wedge cluster-randomized trials with more than two levels of clustering. Clinical Trials 2019;16:225-236.
  • Kasza J, Hooper R, Copas A, Forbes AB. Sample size and power calculations for open cohort longitudinal cluster randomized trials. Stat Med 2020;doi:10.1002/sim.8519.
  • Li F. Design and analysis considerations for cohort stepped wedge cluster randomized trials with a decay correlation structure. Stat Med 2020;39:438–455.
  • Zhou X, Liao XM, Kunz LM, et al. A maximum likelihood approach to power calculations for stepped wedge designs of binary outcomes. Biostatistics 2020;21:102-121.
  • Liu J, Colditz GA. Sample size calculation in three‐level cluster randomized trials using generalized estimating equation models. Stat Med 2020;39:3347-3372.
  • Hemming K, Kasza J, Hooper R, et al. A tutorial on sample size calculation for multiple-period cluster randomized parallel, cross-over and stepped-wedge trials using the Shiny CRT Calculator. Int J Epidemiol 2020;doi:10.1093/ije/dyz237.
  • Harrison LJ, Wang R. Power calculation for analyses of cross-sectional stepped-wedge cluster randomized trials with binary outcomes via generalized estimating equations. Stat Med 2021;doi:10.1002/sim.9205.

Reviews

Systematic reviews of stepped wedge trials:

  • Brown CA, Lilford RJ. The stepped wedge trial design: a systematic review. BMC Med Res Methodol 2006;6:54.
  • Mdege ND, Man MS, Taylor Nee Brown CA, Torgerson DJ. Systematic review of stepped wedge cluster randomized trials shows that design is particularly used to evaluate interventions during routine implementation. J Clin Epidemiol 2011;64:936-48.
  • Beard E, Lewis JJ, Copas A, et al. Stepped wedge randomised controlled trials: systematic review of studies published between 2010 and 2014. Trials 2015;16:353.
  • Davey C, Hargreaves J, Thompson JA, et al. Analysis and reporting of stepped wedge randomised controlled trials: synthesis and critical appraisal of published studies, 2010 to 2014. Trials 2015;16:358.
  • Barker D, McElduff P, D’Este C, Campbell MJ. Stepped wedge cluster randomised trials: a review of the statistical methodology used and available. BMC Med Res Methodol 2016;16:69.
  • Martin J, Taljaard M, Girling A, Hemming K. Systematic review finds major deficiencies in sample size methodology and reporting for stepped-wedge cluster randomised trials. BMJ Open 2016;6:e010166.
  • Grayling MJ, Wason JM, Mander AP. Stepped wedge cluster randomized controlled trial designs: a review of reporting quality and design features. Trials 2017;18:33.
  • Taljaard M, Hemming K, Shah L, et al. Inadequacy of ethical conduct and reporting of stepped wedge cluster randomized trials: Results from a systematic review. Clin Trials 2017;14:333-341.

More

Additional resources, journal references and other information on stepped wedge trials for researchers can be found here.