Validation of HLAMatchmaker algorithm in identifying acceptable HLA mismatches for thrombocytopenic patients refractory to platelet transfusions

BACKGROUND: HLAMatchmaker (HLAMM) is an algorithm that determines donor-recipient histocompatibility based on HLA type. This study determines the effectiveness of HLAMM in identifying suitable platelet (PLT) donors for refractory patients. STUDY DESIGN AND METHODS: Data from a previous prospectively randomized multicenter study comparing cross-reactive group (CREG)-matched versus serologic crossmatch-selected PLT transfusions in refractory patients were analyzed. By use of HLAMM, the compatibility of donor-recipient pairings was determined as the number of donor triplet mismatches (TMMs) and eplet mismatches (EMMs) and compared against the posttransfusion PLT corrected count increment (CCI). The data included 73 patients who received up to two CREG-matched and crossmatch-selected PLT transfusions each (214 transfusions analyzed). RESULTS: TMM and EMM values correlated well with CREG match grade. A and BU matches had TMM and EMM values of 0; BX matches had TMMs and EMMs of 4 and 6 respectively; and C and D matches had TMMs of 10 to 21 and EMMs of 13 to 24. Fewer mismatches (TMM or EMM) predicted better transfusion outcomes (p < 0.05). The median 1-hour CCI was 8000 with TMMs of not more than 9 versus 6000 with TMMs of more than 9. The median 1-hour CCI was 7954 with EMMs of not more than 11 versus 6356 with EMMs of more than 11. The positive predictive value of the different methods in producing a 1-hour CCI of more than 7500 were comparable: TMM, 56 percent; EMM, 54 percent; CREG, 50 percent; and crossmatching, 45 percent (p > 0.05). CONCLUSIONS: HLAMM (both TMM and EMM) successfully identified donors associated with good transfusion outcomes in refractory recipients and represents an acceptable method of choosing donors for refractory patients.