The process of selecting blood donors is crucial for keeping the health of donors and ensuring the safety of the blood supply. However, it may create unpleasant feeling in those who are deferred. In this study, we aim to explore the return rates of Iranian deferred donors in comparison with eligible donors.

The study included all whole blood donors referred between March 2017 and March 2018, who experienced temporary deferral for any reason. Donors who successfully donated blood during this period were also part of the study. Participants were followed up until their next donation attempt, spanning 4.8 years after initial inclusion. Then odds of return and median return time for both deferred and eligible donors were calculated.

From 993,824 volunteers, 733,153 (73.77%) were eligible and 192,332 (19.35%) temporary deferred. The return rate in the eligible and deferred donors was 74.77% vs. 51.77%, respectively (OR:2.78; 99%CI: 2.71–2.81). Odds of return among deferred regular (OR = 7.02, 99%CI:6.64–7.42), men (OR: 2.57, 99%CI:2.45–2.69), and over 45 years (OR: 1.15, 99% CI: 1.09–1.20), was higher than first-time, women, and younger donors. The median return time for eligible and deferred donors was 315 (99%CI: 313–316) and 1,467(99%CI: 1,412–1,524) days, respectively.

This study revealed the negative effect of deferral on the return rate, that led to a 23% reduction in the return of deferred donors. Avoiding unnecessary deferral through adherence to the standard operating procedure of donor selection and effective counselling which clarifies the purpose of deferral and encourages them to return after the deferral period ends are recommended.