Improving recruitment and retention of people with Parkinson's disease to clinical studies: A scoping review.

Background: Timely recruitment and effective retention of participants are challenging for clinical Parkinson's disease (PD) research studies. Not achieving this can affect delivery costs and bias results.

Objective: To identify successful recruitment and retention methodologies for clinical research studies in PD.

Methods: We conducted a systematic scoping review using a Population, Intervention, Comparator, Outcome and Study design (PICOS) framework to search and screen literature within five databases for published quantitative and mixed methods studies evaluating recruitment and retention strategies of interventional and observational trials in PD.

Results: Searches identified 4608 records, of which six papers covering eight studies were included in the review following screening for eligibility. No papers on retention strategies were found that met eligibility criteria. Effective strategies for rapid recruitment included research registries and trial finders (n = 3), digital marketing campaigns (n = 3), site recruitment support (n = 1) and multiple referral sources (n = 1). Recruitment diversity was increased by online campaigns, mandatory 10% minority targets set by funders and supplemental site funding.

Conclusions: This scoping review has identified methods that can be used to increase the rate and diversity of recruitment to PD clinical studies. Retention methodologies are under-researched.