Identifying ethical issues in stepped-wedge cluster randomized trials to inform the Ottawa Statement update: a systematic review of trials published 2016-2022

We reviewed 160 stepped-wedge cluster randomized trials (SW-CRTs) published between 2016 and 2022. These trials often evaluate multifaceted interventions delivered at the cluster- or professional-level rather than individual-level, and most had to rely on at least some form of primary data collection. Although almost all SW-CRTs reported ethics review, fewer than half explained why they used the SW-CRT design, and a substantial minority did not include a statement about whether participant informed consent was obtained. Rarely did consent statement pertain to healthcare providers; most statements pertained to patients. Among the SW-CRTs that had consent statements pertaining to patients, almost half reported not obtaining or waiving consent from them, and many of these did not report clear reasons for this. Our findings highlight the need for clearer guidance in the forthcoming update to the Ottawa Statement on the Ethical Design and Conduct of CRTs.