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#65
HLAMATCHMAKER-DRIVEN ANALYSIS OF RESPONSE TO HLA MATCHED PLATELET TRANSFUSIONS.
A. Nambiar , S. Adams , J. Reid , J. Oblitas , S. Leitman , R. Duquesnoy , D. Stroncek and F. Marincola . USA NIH, Dept Transfusion Medicine and Pittsburgh PA, USA, UPMC, Dept Pathology .

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HLAMatchmaker (HLAM) was used to analyze responses to HLA matched platelet transfusions received by a 60 yr old aplastic anemia patient with HLA alloantibodies. Pre- and post-platelet count data were available on 82/93 transfusions given over a 1-year period. 68 transfusions (from 41unique donors) were from HLA compatible donors and these were further analyzed. Sequence-based typing (SBT) was carried out on the patient and on 36/41 donors. An unambiguous SBT was determined for all except 8 donors. Only low resolution molecular typing results were available for the remaining 5 donors. The serological equivalents were determined using the 2001 HLA dictionary and HLAM Version SER 1.3 was used to determine the total triplet mismatches (TTM) and highly immunogenic triplet mismatches (HITM) for the HLA- A/B loci for each donor-recipient pair. Corrected count increments (CCIs) for all transfusions were correlated with either the number of HITM or the number of TTM. When transfusions were sorted based on whether they had 0-4 (n=44) or 5-10 (n=24) HITM, the mean CCIs were 9.04 ± 3.19 and 7.43 ± 2.75 respectively (p= 0.034). As expected, the mean TTM was lower (7.16 vs. 11.88) in the 0-4 HITM group. Comparison of transfusions with ≤ 8 (n=34) or 9-16 (n=34) TTM showed mean CCIs of 9.11 ± 3.47 and 7.83 ± 2.61 respectively (p=0.089). Although HLA compatible platelet donors were chosen based on CREG matching, HLAM was able to select from among such donors, those with a likelihood of better transfusion outcomes. In our patient, transfusions from donors with 0-4 HITM yielded significantly higher increments when compared to donors with 5-10 HITM. Used prospectively, HLAM can refine platelet donor selection for alloimmunized patients.