Recruitment and implementation challenges are common in stepped-wedge cluster randomized trials: results from a methodological review

International audience ; To explore challenges in recruitment and intervention implementation in recent stepped-wedge cluster randomized trials (SW-CRTs). Study design and setting: We searched PubMed to identify primary reports of SW-CRTs (2019-2020). Two reviewers independently screened studies and extracted data from each report. Recruitment challenge was defined as planned number of clusters or participants not achieved, or any reported changes made to the design to address recruitment difficulties. Implementation challenge was defined as early, late or no implementation of the intervention in at least one cluster. Results: Of 55 SW-CRTs, 18 (33%) had a recruitment challenge, 23 (42%) had none, and for 14 (26%) it was impossible to judge. At least one implementation challenge was present in 24 (44%), 8 (15%) had none, and for 23 (42%) it was impossible to judge. Of the 35 (64%) trials with recruitment or implementation challenges, 18 (72%) had one or more modifications of their design, most often a modification of the trial duration. Conclusion: Investigators must be aware of the risks of recruitment or implementation challenges when considering use of a SW-CRT design. Mitigating strategies should be adopted when planning the trial. More transparent reporting of planned and actual design features is required.