Overcoming challenges to successful recruitment of individuals at the earliest stages of disease: An example from Parkinson's disease research

Background/AimsThe Parkinson Progression Markers Initiative (PPMI) is an international, longitudinal, observational study that acquires comprehensive clinical, imaging and genetic data, as well as cerebral spinal fluid (CSF) and blood biological samples from individuals in all stages of Parkinsons disease (PD) to develop biomarkers that accelerate therapeutic development. The effort to enroll a large population of prodromal individuals (participants with PD biomarkers and/or early symptoms) presents an opportunity to share insights for overcoming specific challenges unique to enrollment prior to the onset of typical symptoms. MethodsPaid and earned media, referral cohorts, and individual and community ambassadors were leveraged as recruitment strategies to attract and enroll a broad study population. The success of each strategy was measured as conversion to (i) informed consent, (ii) smell test completion, and (iii) identification of hyposmic individuals. Participants completed an eConsent and questionnaire online, followed by remote smell test screening for Parkinsons risk. Participants with hyposmia were invited to complete dopamine transporter (DAT) imaging. Those who continued to meet eligibility criteria were invited to enroll in the PPMI clinical study, for comprehensive longitudinal follow-up. ResultsOver 1.2 million visits to the smell test website were recorded and 79,837 participants consented to remote hyposmia screening. A smell test was sent to 57,754 participants and completed by 38,419; 6,649 were identified to be hyposmic (as defined by PPMI study cutoffs). DAT imaging was completed by 1,720, with 1,120 identified as eligible for longitudinal follow-up. The greatest number of participants who consented to smell testing came from paid media and social media ads, referral networks (commercial and study partners), and the MJFF community. Overall, 14.4% of participants who completed smell testing were confirmed to be hyposmic. The highest rates of conversion from completed UPSIT to confirmed case of hyposmia occurred with promoted online search results, earned press coverage, and radio ads. ConclusionPPMI provides a useful example of overcoming challenges to enrollment of participants with biomarkers and/or early symptoms (but without typical symptoms) of disease. Important lessons from these data for this study team, and other researchers alike, are to be agile in recruitment strategies, to utilize effective participant engagement approaches, and to prioritize centralized study teams/resources to offload site burden and streamline participant experience.