BACKGROUND The application of a temporary deferral often leads to donor lapse. Contributing factors may be donors not knowing when their deferral ends or not being contacted and asked to return. The aim of this study was to determine the effectiveness of a reminder message notifying donors that their deferral is coming to an end in increasing donors' postdeferral return
rates. We evaluated the optimal time, content, and mode of delivery of the reminder message. STUDY DESIGN AND METHODS Two studies were conducted with deferred donors. Study 1: donors (n = 1676) were randomized to be sent a reminder message at one of three time points (4 weeks before, 1 week before, and 1 week after their deferral ended) or to a no contact control condition. Study 2: donors (n = 1973) were randomized to three message type conditions (emotive email, nonemotive email, nonemotive SMS). Attempted return behavior was extracted (appointments, attendances) at 1 month. RESULTS In Study 1, being sent the reminder message increased odds of donors attempting to return within 3 months compared with the control group (OR:2.01). Sending the reminder 1 week before the deferral ended was the most effective time point. In Study 2, the nonemotive message increased the odds of attempting to return compared with the emotive message (OR:1.38). No differences were found between email and SMS messages. DISCUSSION Sending a reminder message to donors when their deferral is coming to an end is a simple, effective, and cost-effective method to retain donors.