Blood Donation Deferral at a Tertiary Centre in Riyadh: Epidemiology, Sex-Specific Patterns, and Donor Retention Outcomes

Background: Blood donation deferral poses a significant challenge to transfusion services worldwide, threatening blood supply adequacy and donor retention. Population-specific data on deferral epidemiology and subsequent donor return behavior in Saudi Arabia remain limited. This study aimed to characterize the prevalence, reasons, and demographic patterns of blood donation deferral at King Fahad Medical City (KFMC)—a major quaternary referral center in Riyadh—and to quantify the rate at which temporarily deferred donors re-engage with the donation process at the encounter level. Methods: A retrospective observational study was conducted on records of all registered volunteer blood donor encounters at KFMC from 1 January 2023 to 31 December 2024 (n = 60,290), extracted from the Hematos IIG blood bank information system. Donor demographics (age, sex, weight, nationality), deferral classification (temporary, permanent, indeterminate), deferral reason, pre-deferral donation frequency, and post-temporary-deferral donation frequency were analyzed. Inferential statistics employed the Chi-square test and Fisher’s exact test (significance threshold: p < 0.05). A multinomial logistic regression, restricted to the 10,681 encounters classified as temporarily deferred, identified correlates of post-deferral donation frequency, adjusted for donation frequency before deferral. Results: Of 60,290 registered donor encounters, 18,458 (30.6%) resulted in deferral. Male donors constituted 86.4% of deferrals; the 31–45-year age group accounted for 47.3%. The three leading deferral reasons were abnormal vital signs (39.4%), post-donation transfusion-transmitted infectious disease (TTID) screening reactivity (35.6%), and low hemoglobin (14.0%). Sex-stratified analysis revealed that among female donors, low hemoglobin (40.50%) exceeded abnormal vital signs (35.50%) as the leading reason. Among the 10,681 encounters classified as temporarily deferred, 86.70% did not return to donate within the observation window. In a multinomial regression restricted to this subgroup, donation frequency before deferral was the strongest correlate of return (OR 21.02, 95% CI 14.94–29.58 for three or more subsequent donations among donors with ≥3 prior donations vs. none), and deferral for abnormal vital signs was also associated with higher odds of return (OR range 3.55–4.60, all p < 0.001). Conclusions: Nearly one-third of blood donor encounters at this tertiary center resulted in deferral, with abnormal vital signs and TTID screening reactivity as the predominant reasons. The low re-engagement rate (13.30%) among temporarily deferred donors underscores a need for structured follow-up programs, particularly for first-time donors, for whom an established donation history was the strongest predictor of return. Sex-specific interventions—targeting hemoglobin optimization in female donors and cardiovascular risk factor awareness in male donors—are warranted to reduce the deferral burden and safeguard the blood supply.