Logistic, ethical, and political dimensions of stepped wedge trials: Critical review and case studies

Audrey Prost*, Ariella Binik, Ibrahim Abubakar, Anjana Roy, Manuela De Allegri, Christelle Mouchoux, Tobias Dreischulte, Helen Ayles, James J. Lewis, David Osrin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

59 Citations (Scopus)


Background: Three arguments are usually invoked in favour of stepped wedge cluster randomised controlled trials: the logistic convenience of implementing an intervention in phases, the ethical benefit of providing the intervention to all clusters, and the potential to enhance the social acceptability of cluster randomised controlled trials. Are these alleged benefits real? We explored the logistic, ethical, and political dimensions of stepped wedge trials using case studies of six recent evaluations. Methods: We identified completed or ongoing stepped wedge evaluations using two systematic reviews. We then purposively selected six with a focus on public health in high, middle, and low-income settings. We interviewed their authors about the logistic, ethical, and social issues faced by their teams. Two authors reviewed interview transcripts, identified emerging issues through qualitative thematic analysis, reflected upon them in the context of the literature, and invited all participants to co-author the manuscript. Results: Our analysis raises three main points. First, the phased implementation of interventions can alleviate problems linked to simultaneous roll-out, but also brings new challenges. Issues to consider include the feasibility of organising intervention activities according to a randomised sequence, estimating time lags in implementation and effects, and accommodating policy changes during the trial period. Second, stepped wedge trials, like parallel cluster trials, require equipoise: without it, randomising participants to a control condition, even for a short time, remains problematic. In stepped wedge trials, equipoise is likely to lie in the degree of effect, effectiveness in a specific operational milieu, and the balance of benefit and harm, including the social value of better evaluation. Third, the strongest arguments for a stepped wedge design are logistic and political rather than ethical. The design is advantageous when simultaneous roll-out is impractical and when it increases the acceptability of using counterfactuals. Conclusions: The logistic convenience of phased implementation is context-dependent, and may be vitiated by the additional requirements of phasing. The potential for stepped wedge trials to enhance the social acceptability of cluster randomised trials is real, but their ethical legitimacy still rests on demonstrating equipoise and its configuration for each research question and setting.

Original languageEnglish
Article number351
Issue number1
Publication statusPublished - 17 Aug 2015

Bibliographical note

Funding Information:
This article is part of a special collection on stepped wedge trials. Contributions from LSHTM authors form part the work of the LSHTM Centre for Evaluation, which aims to improve the design and conduct of public health evaluations through the development, application and dissemination of rigorous methods, and to facilitate the use of robust evidence to inform policy and practice decisions. We thank other members of our writing group, including James Hargreaves, Katherine Fielding, Rumana Omar, Gianluca Baio, Jennifer Thompson, Sam Ononge, Calum Davey and Emma Beard, for their input during the development of this article. We received no dedicated project funding for this work. D Osrin is funded through a Wellcome Trust Senior Research Fellowship in Clinical Science (091561/Z/10/Z). H.Ayles is funded by the Doris Duke Charitable Foundation for this work (2009060). A Binik’s research is supported by the NIHR Biomedical Research Centre, Oxford. The funding agencies had no role in the study design, collection, analysis or interpretation of data, writing of the manuscript or in the decision to submit the manuscript for publication.

Publisher Copyright:
© 2015 Prost et al.


  • Ethics
  • Methodology
  • Public health
  • Stepped wedge trials


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