Background: Various papers have addressed pros and cons of the stepped wedge cluster randomized trial design (SWD). However, some issues have not or only limitedly been addressed. Our aim was to provide a comprehensive overview of all merits and limitations of the SWD to assist researchers, reviewers and medical ethics committees when deciding on the appropriateness of the SWD for a particular study.
Methods: We performed an initial search to identify articles with a methodological focus on the SWD, and categorized and discussed all reported advantages and disadvantages of the SWD. Additional aspects were identified during multidisciplinary meetings in which ethicists, biostatisticians, clinical epidemiologists and health economists participated. All aspects of the SWD were compared to the parallel group cluster randomized design. We categorized the merits and limitations of the SWD to distinct phases in the design and conduct of such studies, highlighting that their impact may vary depending on the context of the study or that benefits may be offset by drawbacks across study phases. Furthermore, a real-life illustration is provided.
Results: New aspects are identified within all disciplines. Examples of newly identified aspects of an SWD are: the possibility to measure a treatment effect in each cluster to examine the (in)consistency in effects across clusters, the detrimental effect of lower than expected inclusion rates, deviation from the ordinary informed consent process and the question whether studies using the SWD are likely to have sufficient social value. Discussions are provided on e.g. clinical equipoise, social value, health economical decision making, number of study arms, and interim analyses.
Conclusions: Deciding on the use of the SWD involves aspects and considerations from different disciplines not all of which have been discussed before. Pros and cons of this design should be balanced in comparison to other feasible design options as to choose the optimal design for a particular intervention study.