What is a stepped wedge trial? A stepped wedge trial is a crossover trial in which interventions are implemented according to a staggered timetable over several time periods. The trials are mostly cluster randomized, with the intervention being delivered at some geographical, service, or another cluster level. The crossover is unidirectional, i.e., a sequence may switch from treatment condition B to A but never vice versa (Figures 1, 2).
Variations in design Several variations in the design exist for step wedge trials. Figure 1 illustrates a typical stepped wedge design with two randomized sequences and five time periods, while figure 2 illustrates alternative step wedges schemes. Figure 3 represents the variation in the design with a series of repeated cross-sectional slices through clusters, a continuous period of recruitment or identification marked by dates of intervention, or…
