Professionally designed information materials and telephone reminders improved consent response rates: evidence from an RCT nested within a cohort study

OBJECTIVES: To investigate whether different study-to-participant communication methods increase response, increase response from hard-to-engage individuals, and influence participants' consent decisions. STUDY DESIGN AND SETTING: A randomized controlled trial within the Avon Longitudinal Study of Parents and Children. Cohort members were invited to re-enroll at age 18 and consent to linkage to their health and administrative records. Participants were randomized to receive one of eight combinations of three interventions: a prior-notification postcard or no contact, a standard or professionally designed consent pack, and a phone or postal reminder. The primary outcome was return of the consent form (“response”), with consent decision being the secondary outcome. RESULTS: Of 1,950 participants, 806 (41%) responded. Response rates were 2.7% higher (95% confidence interval: −0.06, 5.5%; P = 0.06) among those receiving designed packs than among those receiving standard packs and 6.4% higher (2.3, 10.6%; P = 0.002) among those receiving phone reminders (compared with postal reminders). The prior-notification postcard did not influence response rates [difference = 0% (−2.8, 2.8%; P = 1.0)], and we found no evidence that the communication method influenced consent decision. CONCLUSION: This trial provides evidence that communication material design can influence response rates and that phone reminders have superior cost/benefit returns over designed materials. Experimental evaluation of communications strategies and dissemination of findings may benefit cohort studies.