Cumulative recruitment experience in two large single-center randomized, controlled clinical trials

Abstract

Background: Trial recruitment is challenging for researchers, who frequently overestimate the pool of qualified, willing participants. Little has been written about recruitment and the comparative success of recruitment strategies. We describe one center's experience with recruitment in two regional single-center clinical trials with a combined total of 1971 participants.

Methods: The heart failure trial was conducted between 1999 and 2003. The asthma trial was performed between 2003 and 2006. Trial databases were queried for referral source of each individual. Data were analyzed for effectiveness of referral source using three measures: percentage of enrollment due to that source, subject commitment to the trial (retention rate), and economics (cost per enrollee).

Results: 47.8% of CHF enrollees came from computer-generated lists or from healthcare provider referrals. Average marketing cost for enrollees and completers was $29.20 and $41.96 respectively. The most economical marketing strategy was self-referral in response to flyers. Most asthma participants (53.5%) were referred from healthcare providers, mailings to lists from local healthcare institutions, or self-referred in response to flyers. Average marketing cost for enrollees and completers was $20.44 and $38.10 respectively. The most economical marketing strategy was patient mailings. Retention rates were not markedly different among referral sources in either trial.

Conclusion: In order to be considered effective, a recruitment strategy must demonstrate a balance between response to recruitment, retention rates, and economics. Despite the differences between these two clinical trials, the most effective recruitment strategies in both trials were mailings to locally-generated, targeted lists, and referrals from healthcare providers.