154-P

Abstract

Aim To determine if adding HLA-DRB1 typing to donors with only HLA-A, B adds unique phenotypes to a Registry of 10 million donors. Methods A cohort of AB only typed donors on the Be The Match Registry ® with stored sample were typed at DRB1. Donors were self described with the broad race/ethnic groups of African American (AFA), Asian Pacific Islander (API), Caucasian (CAU), and Hispanic (HIS). The CAU group carried specific race designation of Mediterranean, Mideast, and/or North Coast of Africa (MENAFC). Once DRB1 results were reported we determined the number of donors in the Registry which carry the same ABDR phenotype. Donors were classified as unique if no other donors on the Registry carried their phenotype and classified as uncommon if one or two donors on the Registry had the potential phenotype. Results Results of the analysis are detailed in the table below. In all race groups, over 25% of the donors carried an uncommon or unique phenotype contributing additional diversity to the Registry. AFA had the highest percent of unique phenotypes with 39.6%. The MENAFC group carried a surprisingly high percentage of unique phenotypes (14.2%) indicating a more diverse and/or underrepresented population in the Be The Match Registry. Interestingly, two donors in this cohort were requested for additional typing by a searching patient less than 3 months after DRB1 typing was completed [ Table 1 ]. Conclusions AB only donors can have significant diversity and should be considered as a possible way to expand the registry with unique or uncommon phenotypes, given otherwise low utilization of AB only typed donors requested for patient searches. Having a diverse registry is crucial for searching patients with unique phenotypes to identify a suitably matched stem cell donor.