Strategies for navigating clinical trial participant recruitment in primary care: a scoping review

Clinical trialists have increasingly partnered with primary care practices (PCPs) to engage potential participants, yet a better understanding of the strategies applied in these settings is needed to support recruitment planning. This study synthesized evidence on recruitment methods for non-communicable disease (NCD) randomized controlled trials (RCTs) to identify practical strategies and tools for researchers and improve collaboration with PCPs. A scoping review was conducted by searching Ovid MEDLINE ® ALL, Embase Classic+Embase, and core databases in Web of Science for articles on PCP RCTs in NCDs. Non-peer-reviewed papers, protocols, proceedings, grey literature and qualitative or observational studies were excluded. Two reviewers screened the studies and completed extraction, with additional reviewers verifying the data. Forty-five studies were included in the review. The findings were synthesized using descriptive analysis and presented in narrative and tabular forms. While mailed letters remain the most common recruitment strategy in PCPs for NCD RCTs ( n = 15), some trials were successful in applying a multilayered approach that combined traditional and technology-mediated communications ( n = 17). This can be complemented by a simplified enrollment process, minimal participant burden and adequate incentives to support recruitment. Four recruitment patterns emerged: (1) Engage PCPs early and provide training to support recruitment; (2) Offer incentives to PCPs and participants; (3) Apply a multi-layered strategy: start with electronic medical records to identify potentially eligible patients then communicate via letters, direct invitations, texts, emails or call reminders; (4) Offer a streamlined consent and enrollment processes for PCPs and participants. This review provides insights into communication strategies that support recruitment planning, potentially helpful for efficient development of trials. Future work may explore digital advertising algorithms and automated communications to support recruitment.