Quantifying the role of communication in recruitment status outcomes for a clinical trial on genetic testing uptake

Participant recruitment remains a significant challenge in clinical trials, often resulting in delays, increased resource expenditures, and missed opportunities for advancing care. While previous research has largely focused on participants' perspectives regarding recruitment barriers, less is known about the influence of different outreach strategies (methods and frequency) from the viewpoint of research staff. This study evaluates the likelihood of reaching a definitive enrollment outcome to inform more effective and resource-efficient recruitment strategies.

Data were obtained from recruitment efforts for a two-phase clinical trial aimed at increasing hereditary cancer genetic testing uptake among eligible individuals. Participant recruitment utilized email invitations for patients in participating practices and multimedia campaigns for the public. Eligible participants received up to two email reminders and 5-8 recruitment calls, with a standardized call survey ensuring consistency.

Of the invited, 2485 (82.8%) accessed the email link and completed the eligibility screening survey, of these 80.4% of invitees reached a definitive recruitment status outcome: ineligible (37.2%), refused (15.6%), consented (27.6%), while 19.5% were lost to enrollment. Analysis of call attempts revealed that call attempt one had the highest participant answer rate (∼45%), which declined with each additional attempt, reaching 13% at six or more attempts. Email outreach alone produced probability spikes in definitive outcomes following email reminders. Additional calls demonstrated sharply diminishing returns beyond the fourth to sixth attempts.

This study demonstrates that tracking and optimizing outreach frequency, timing, and mode can enhance clinical trial recruitment efficiency. Specifically, at least one email and one phone call significantly improve the likelihood of reaching a definitive recruitment outcome, while exceeding 4-6 call attempts yields minimal additional benefit. These findings provide a framework for recruitment strategies, enabling more effective allocation of resources and increasing the chances of meeting recruitment goals in future clinical trials.