Grand rounds in methodology: improving the design of staggered implementation cluster randomised trials

The stepped-wedge cluster randomised trial is a popular design in implementation and health services research. All clusters, such as clinics or hospitals, start in the control state, and gradually switch over to treatment in a random order until all clusters have received the intervention. The design allows for the incorporation of an experiment into the gradual roll-out of an intervention across clusters. However, the traditional stepped-wedge layout may not be the best choice in many scenarios. In this article, we discuss modifications to the stepped-wedge design that maintain a staggered roll-out, but which may improve some key characteristics. We consider improving the timing of implementation periods, reducing the volume of data collection and allowing for the recruitment of clusters over the course of the trial.