Recruitment, retention and reporting of variables related to ethnic diversity in randomised controlled trials: an umbrella review

Objective This umbrella review synthesises evidence on the methods used to recruit and retain ethnically diverse participants and report and analyse variables related to ethnic diversity in randomised controlled trials.Design Umbrella review.Data sources Ovid MEDLINE, Ovid Embase, CINAHL, PsycINFO and Cochrane and Campbell Libraries for review papers published between 1 January 2010 and 13 May 2024.Eligibility criteria English language systematic reviews focusing on inclusion and reporting of ethnicity variables. Methodological quality was assessed using the AMSTAR 2 tool.Results Sixty-two systematic reviews were included. Findings point to limited representation and reporting of ethnic diversity in trials. Recruitment strategies commonly reported by the reviews were community engagement, advertisement, face-to-face recruitment, cultural targeting, clinical referral, community presentation, use of technology, incentives and research partnership with communities. Retention strategies highlighted by the reviews included frequent follow-ups on participants to check how they are doing in the study, provision of incentives, use of tailored approaches and culturally appropriate interventions. The findings point to a limited focus on the analysis of variables relevant to ethnic diversity in trials even when they are reported in trials.Conclusion Significant improvements are required in enhancing the recruitment and retention of ethnically diverse participants in trials as well as analysis and reporting of variables relating to diversity in clinical trials.PROSPERO registration number CRD42022325241.