RECRUITMENT METHODS AND RETENTION IN RESEARCH STUDIES OF HARD-TO-REACH COMMUNITIES MARGINALISED DUE TO DISCRIMINATION, AND SOCIAL STIGMATIZATION: A SYSTEMATIC REVIEW

OBJECTIVES Recruiting hard-to-reach and marginalized populations into health-related research studies can be challenging. This systematic review aimed to synthesize evidence on the identification and effectiveness of different recruitment and retention methods for marginalized communities. METHODOLOGY Seven databases (PubMed, MEDLINE, EMBASE, Web of Science, Scopus, PsycINFO, and Proquest (Including Google Scholar for grey literature) were searched from January 1950 to June 2022 for studies recruiting marginalized groups and detailing recruitment and retention methods. Study details, population, recruitment and retention methods, outcomes, and limitations were extracted. The frequency of recruitment and retention methods was tallied, and narrative synthesis was conducted. RESULTS Of the 101 studies included, thirty-one studies met the inclusion criteria, covering populations including lesbian, gay, bisexual, and transgender (LGBT), racial and ethnic minorities, immigrants, and low socioeconomic groups. The most common recruitment methods were respondent-driven sampling (n=9), social media/online advertising (n=8), snowball sampling (n=7), and community outreach (n=6). Recruitment rates ranged from 2% to 91%, where reported. CONCLUSION Engaging minority communities involved direct community outreach methods such as presentations, health fairs, and in-person contact. Common retention strategies included financial incentives, culturally competent staff, and active engagement, yet no single method consistently proved most effective. Utilising a combination of tailored sampling approaches can mitigate the limitations inherent in individual methods. Enhanced reporting on recruitment and retention rates is essential for future studies.