An Embedded Recruitment Trial of Behavioral Economic Strategies to Improve Enrollment Rates in Clinical Research (Preprint)

BACKGROUND Nearly 1 in 3 clinical trials end prematurely due to under-enrollment. Strategies to enhance recruitment are often implemented without scientific rigor to evaluate efficacy or cost-effectiveness. OBJECTIVE This study evaluated two behavioral economic strategies to improve enrollment and retention rates: information provision (IP) and contingency management (CM; i.e., lottery) across four clinical trials. METHODS A sample of 212 participants were enrolled across four clinical trials focused on tobacco use, HIV, and/or neuroimaging (NCT03169101, NCT03384784, NCT03438188, NCT02837510). The CM condition included a lottery: for each study visit completed, participants received 5 “draws” from a bowl containing 500 “chips” valued at $0, $1, $5, or $100. In the IP condition, text messages that targeted injunctive norms about research (e.g., “Many find it a rewarding way to advance science and be part of a community”) were sent via the Way to Health Platform before all study visits. Participants were randomized to 1 of 4 conditions: IP, CM, IP+CM, and standard recruitment (SR). We performed logistic regression, controlling for sex and study, with condition as a between-subject predictor. Outcomes were percentage who met final eligibility (FE; primary) and intent-to-treat criteria (ITT; secondary). RESULTS Results: Rates of meeting FE and ITT status were: 42.9% and 33.9% for IP+CM; 30.9% and 18.2% for IP only; 20.8% and 18.9% for CM only; and 25% and 12.5% for SR, respectively. In the logistic regressions, females were more likely to meet FE and ITT status than males (ORs= 2.0 and 2.7, respectively, P=.04 and .01, respectively). Although not significant, the IP+CM group was twice as likely to achieve FE status than the SR group (OR=2.3, 95%CI 0.96, 5.4, P=.06). The IP+CM group was significantly more likely to reach ITT status than the SR condition (OR= 3.9, 95%CI 1.3, 11.1, P=.01). Follow-up models suggested that those who received the IP condition (controlling for CM) were significantly more likely to reach FE status (OR=1.9, 95%CI 1.0, 3.6, P=.04). However, CM (controlling for IP) accounted for increased likelihood to reach ITT status (OR=2.3, 95% CI 1.1, 4.7, P=.03). CONCLUSIONS Combining IP and CM strategies may improve rates of recruitment and retention. IP appeared to have increased enrollment, while CM increased retention rates. Evidence from this study provides support for the utility of behavioral economics strategies to improve enrollment and reduce attrition in clinical trials.