(P-PB-1) Probability of finding partially or fully compatible blood for patients with sickle cell disease: A descriptive analysis of donor-recipient genotype data

Background/Case Studies: Alloimmunization substantially increases the risk of future hemolytic transfusion reactions. Alloimmunization can be prevented by transfusing fully matched RBC units, which is made easier by advances in RBC genotyping. This study aimed to estimate the probability of finding a perfect match between the blood of a patient with sickle cell disease (SCD) and the blood of regular donors or donors with rare blood. Moreover, the impact of a simulate intensive recruitment campaign of new donors (+1000) from the general population was performed.

Study

Design/Methods: Blood donors and patients with SCD were first identified in separate databases. Specifically, the genotype and phenotype data of active donors (N=194,853 – 91.0% White, 1.2% Black and 7.8% other; i.e., who donated at least once from 01-01-2019 to 21-12-2021) and rare blood donors (N=708) were obtained (database compiled and updated by the provincial reference laboratory). Since December 2020, all donors are phenotyped for C,E, c,e and K antigens (Ag). Data from a cohort of SCD patients previously genotyped (N=270) were also obtained. The probability of a perfect donor-recipient match was then based on the recorded phenotype (deduced from genotype data) for the ABO, Rh (D, C, E or C/c, E/e), K, Fya, Fyb, V, VS, and hrB Ags.

Results/Findings: When considering only ABO, D, C, E and K Ags, the probability of a perfect match was 100.0% with the active and rare donor databases (combined). However, when additionally considering c and e, this probability dropped to 69.3% with the active donor database (alone) and to 78.1% with the active and rare donor databases (combined; Table 1). Finally, when considering all Ags (i.e., adding Fya, Fyb, V, VS, hrB), the probability of a perfect match was only 0.5% with the active donor database (alone) and 23.9% with the active and rare donor databases (combined). Adding 1000 simulated fully typed donors (based on Ag frequencies observed in the active donors) was estimated to increase this probability to a mean of 42.5% (standard deviation=15.8%).

Conclusions: When considering only the ABO, D, C, E, and K Ags, the probability of finding a perfect match for a patient with SCD approaches 100%. However, this probability substantially decreases with the number of Ags considered. The addition of 1000 new donors would increase the probability of a perfect match (for all Ags) from 23.9% to 42.5%, suggesting that intensive donor recruitment campaigns followed by comprehensive genotyping/phenotyping are a sound approach to improving the odds of a perfect match.

Importance of research: This study estimated the probabilities of finding compatible blood for patients with sickle cell disease, and thus informs future donor recruitment strategies. Moreover, the large impact of a (simulated) donor recruitment campaign supports the effectiveness of this approach to improve the odds of a perfect donor-recipient match.