Background: Blood donors who deferred for blood donation temporally interrupts the donation pathway and some otherwise willing donors do not return once they become again eligible. We evaluated a simple donor-specific smartphone-calendar reminder combined with later telephone follow-up.

Methods: The prospective cohort included 214 temporarily deferred donors. A reminder was entered in the donor’s smartphone calendar for the date of renewed eligibility. Approximately one month after becoming eligible again, donors were contacted by telephone to ascertain subsequent donation. A same-centre historical cohort of 214 temporarily deferred donors managed without smartphone-calendar installation was used for comparison. The primary outcome was subsequent confirmed blood donation.

Results: Forty-five of 214 intervention donors returned (21.03%; 95% CI 16.1-27.0), compared with 18 of 214 historical controls (8.41%; 95% CI 5.4-12.9). The absolute difference was 12.62 percentage points, with a risk ratio of 2.50 (95% CI 1.50-4.17) and an odds ratio of 2.90 (95% CI 1.62-5.20); Fisher exact p=0.0003. Return occurred in 37/183 men and 8/31 women. Age-specific return was 12/33, 20/73, 11/83, 1/19 and 1/6 across the five age groups from 18-24 to 55-65 years. By deferral duration, 22/89, 16/73, 5/38 and 2/14 donors returned in the 1-7, 8-30, 31-90 and >90-day groups. In the existing exploratory complete-case model (n=195), repeat donor status was associated with higher odds of return (adjusted OR 2.25, 95% CI 1.04-4.89; p=0.040), while longer deferral duration was associated with lower odds of return (adjusted OR 0.98 per day, 95% CI 0.97-1.00; p=0.020).

Conclusion: An individualized smartphone-calendar reminder among the temporary deferred donors incorporated into a follow-up pathway was associated with a higher observed subsequent-donation proportion than that seen in an equal-sized same-centre historical cohort.