Batched stepped wedge design
RECRUITMENT
Large clinical trials are notoriously complex to deliver and can have prolonged timelines. Surgical researchers are increasingly interested in methodological developments in randomised trials [The EAGLE protocol suggested indicatively that 7 batches of around 48 clusters each might be run, but the design and approach to analysis (meta-analysis across batches) gave us the flexibility to have batches of varying sizes. The make-up of a batch was determined largely by the order in which clusters enrolled, but again the design and meta-analytic approach gave us the flexibility, if we wanted it, to focus the recruitment of clusters to different batches in different global regions, for example. The sample size target (see below) was based on the total number of clusters and total number of surgical procedures across all batches.