(P-PB-15) What Can We Learn from Analyzing Rare Blood Requests That Could Not Be Filled?

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 to fulfill requests for specific patient needs. From 2017 to 2024, the annual fulfillment rate, defined as the % of requests fulfilled or partially fulfilled, ranged from 94% to 97%. We analyzed the requests that were unfulfilled during this period.

Study

Design/Methods: The ARDP request log was sorted by fulfilment status and unfulfilled requests were categorized by ABO type, the type of rare product requested. Rare red blood cell (RBC) types include those lacking high prevalence antigens (HiPrev), some of which are “exquisitely rare phenotypes (ERP), or those lacking multiple common antigens (PhenoRare) or RH allele selected (RAS) RBC units. Patient outcomes, when provided, were examined.

Results/Findings: During the 8-year period (2017 to 2024), there were 8012 requests for rare blood products, of which 162 (2.0%) were unfulfilled. Of these, 60% were for group O patients. The majority (76%) of unfulfilled requests were for RBC units lacking HiPrev antigens, with 33% of these being ERP [At(a-), En(a-), Er(a-), GE:-3, Jk:-3, Ko, Rh:-46 and XK:-1]. In some cases [ex. En(a-)] there were no registered donors with the requested phenotype. Of the unfilled requests, 17% were for RAS units, of which 15 (nearly 10%) were for E- hr^S- (Rh:-19) units. Twenty-eight requests were for RBC units lacking the U antigen, 21 of these were Group O with 16 of these were Group O RhD-, 11 of these requests were for a single Group O RhD+ patient with anti-D. Half of the U- requests required C-E-K- phenotype with some requiring additional antigens. Of the 139 (85%) unfilled requests where outcome information was provided, two-thirds of patients were not transfused, including 6 pregnant women who delivered without incident. In 24% of cases with outcomes information, the patient was transfused units in which one or more antigens were not matched. Nine patients were reported to have expired or were transferred to hospice/palliative care. Auto-donation or directed donation from family members were utilized in 2 cases each.

Conclusions: Although the ARDP is successful in locating rare blood products for the great majority of requests received, there are cases where units are not obtained. Three-fourths of unfulfilled requests were for HiPrev phenotypes, with the most frequently requested HiPrev phenotype being U-. Outcome information was provided for most unfilled requests and for these, the most common decision (65%) made when compatible blood could not be located was to not transfuse red cells. In a quarter of cases, the clinical team changed the request to drop the requirement for an antigen to be negative such that the revised request could be fulfilled.