Telephone reminders are effective in recruiting nonresponding patients to randomized controlled trials

Objective: Studies investigating means of recruiting participants to randomized controlled trials (RCTs) are sparse. We investigated the effects of telephone reminders as a recruitment strategy. Study Design and Setting: Sick-listed employees received a written invitation to participate in a study comparing standard treatments with a solution-focused follow-up and were randomly allocated to an intervention or control group (n = 703). Those who did not respond within 2 weeks received either 'no reminder' (n = 242) or 'attempted telephone reminder' (n = 256). Outcome was enrollment to the RCT. Results: An intention to recruit analysis revealed no significant differences between the groups (P =.229). An intention to phone analysis among nonresponders revealed significant differences between 'no reminder' (recruited 4.5%) and 'attempted telephone reminder' (recruited 12.1%) (P =.003, odds ratio 2.89, 95% confidence interval [CI] 1.42-5.90). An analysis of numbers needed to phone showed that to recruit one more person in this group of nonresponders, we needed to phone 13 persons (95% CI = 8-33). Conclusion: Systematic use of telephone calls can increase the recruitment rate among nonresponders in RCTs. (C) 2004 Elsevier Inc. All rights reserved.