(P-BC-88) What Can We Learn from Analyzing Rare Blood Requests Fulfilled with Frozen Red Cell Units?

Background/Case Studies: The American Rare Donor Program (ARDP) currently has more than 110,000 active rare blood donors. ARDP staff facilitate locating rare blood products and recruiting rare blood donors to fulfill requests for rare blood for specific patient needs. In recent years, ARDP receives more than one-thousand requests for rare blood products and ships more than 2000 rare red blood cell (RBC) units annually. We analyzed the requests that were fulfilled over a two-year period to evaluate those that were fulfilled with frozen RBC products.

Study

Design/Methods: The ARDP request log was sorted by fulfilment status and type of product shipped (liquid or frozen RBC units) were categorized by the type of rare product requested – Fulfillment with liquid vs frozen products was examined based on rare type – high-prevalence antigen negative (HiPrev) including exquisitely rare phenotypes (ERP) for which there are ≤10 registered donors, RBC units lacking multiple common antigens (PhenoRare) or RH allele selected (RAS) RBC units.

Results/Findings: In calendar year (CY) 2023 and CY2024, ARDP received more than 2400 requests for red blood cell (RBC) units and shipped more than 2700 rare RBC units. Table 1 provides details. A significant proportion of all requests for rare RBCs were fulfilled with at least 1 frozen unit (12.7% in CY2023, 11.9% in CY24). The percentage of units shipped that were frozen was similar (10.6% in CY2023, 10.4% in CY2024). Of the frozen RBC units shipped, the majority were HiPrev (64% in CY2023, 65% in CY2024). The requests for HiPrev phenotypes that were fulfilled with at least 1 frozen RBC unit included U-, PP1Pk-, D--, Vel- and Yt(a-) phenotypes. The percentage of frozen units that broke was small (< 5%) in both years.

Conclusions: In the two-year period analyzed, frozen RBC units were utilized to fulfill more than 10% of rare RBC units requested through the ARDP. The majority of frozen units shipped were HiPrev phenotypes, though frozen PhenoRare and RAS RBC units were also utilized to fulfill rare blood requests. These data demonstrate the criticality of the frozen rare RBC inventory at blood centers in the US.