Undertaking studies within a trial to evaluate recruitment and retention strategies for RCTs:lessons learnt from the PROMETHEUS research programme

Background Randomised controlled trials (‘trials’) are susceptible to poor participant recruitment and retention. Studies Within A Trial (SWATs) are the strongest methods for testing the effectiveness of strategies to improve recruitment and retention. However, relatively few of these have been conducted. Aims PROMoting THE USE of Studies Within A Trial (PROMETHEUS) aimed to facilitate at least 25 SWATs evaluating recruitment or retention strategies. We share our experience of delivering the PROMETHEUS programme, and the lessons learnt for undertaking randomised SWATs. Design A network of 10 Clinical Trials Units (CTUs) and one primary care research centre committed to conducting randomised controlled SWATs of recruitment and/or retention strategies was established. Promising recruitment and retention strategies were identified from various sources including Cochrane systematic reviews, the SWAT Repository, and existing prioritisation exercises, which were reviewed by patient and public (PPI) members to create an initial priority list of seven recruitment and eight retention interventions. Host trial teams could apply for funding and receive support from the PROMETHEUS team to undertake SWATs. We also tested the feasibility of undertaking coordinated SWATs, across multiple host trials simultaneously. Setting CTU-based trials recruiting or following up participants in any setting in the UK were eligible. Participants CTU-based teams undertaking trials in any clinical context in the UK. Interventions Funding of up to £5,000 and support from the PROMETHEUS team to design, implement, and report SWATs. Main outcome measures Number of host trials funded