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ANALYSIS OF PLATELET INCREMENTS IN HLA ALLOIMMUNIZED PATIENTS VERIFIES THE HLAMATCHMAKER ALGORITHM.
Ashok Nambiar, Sharon Adams, Jaime Oblitas, Susan Leitman, Rene Duquesnoy, David Stroncek and Francesco Marincola. Bethesda MD, USA, NIH, 20892, Transfusion Medicine and Pittsburgh PA, USA, UPMC, 15211, Pathology.

We used HLAMatchmaker (HLAM) to analyze transfusion responses in 16 HLA alloimmunized aplastic anemia patients receiving long-term support with HLA-matched platelets. Corrected count increments (CCIs) were calculated for 647/964 transfusions with pre- and post transfusion platelet counts. Molecular HLA -A and -B typing data of patients and donors was retrieved; sequence-based typing was done on 8 patients. We analyzed 523/647 transfusions, excluding those with only serological types. HLAM identified additional, HLA-compatible antigens [up to 3 triplet mismatches (TM)]. 18 (median) ‘acceptable’ donor antigens were identified for each patient; 5 (median) of which would be excluded by conventional CREG-matching criteria. Median CCIs for CREG-incompatible (n=353) and CREG-compatible transfusions (n=170) were 12.23 and 12.47 respectively (p=0.05). HLAM determined total TM (TTM) and highly immunogenic TM (HITM) at HLA- A/B loci for each donor-recipient pair. 379/523 transfusions had a CCI ≥ 8; this group had medians of 4 HITM and 11 TTM. For transfusions with CCI < 8 (n=144), median HITM and TTM were 6 (p=0.0000002) and 13 respectively (p=0.000005). Based on TM, transfusions were sorted and median CCIs determined. CCIs correlated inversely with the number of mismatched immunogenic triplets. These data corroborate HLA compatibility determinations by HLAM, and support its potential to increase the probability of finding HLA-matched donors for alloimmunized patients.

CCIs for all transfusions
HIMM= 0-4HIMM > 4p value
13.8111.000.000003
TTM= 0-11TTM > 11p value
13.2011.220.004