1.2000
#35-OR
PROBABILITY OF A NEGATIVE CROSSMATCH: A METHOD FOR QUANTITATING SENSITIZATION.
B. Lavingia, CHS, R. Vorhaben, CHS, C. Giang, J. Crumpton, B. Kauper and P. Stastny, MD. Dallas TX, UT Southwestern Med Cntr, Internal Medicine.
HLA immunization assessed by serum screening is usually expressed as panel-reactive antibodies (PRA). However, level of sensitization is poorly reflected in PRA values, which do not consider HLA gene frequencies or take into account individual response profiles. To improve this, we have combined new methods for detection and identification of HLA antibodies with interpretation based on recognition of HLA epitopes. Our analysis incorporated recipient’s self antigens and HLA antigens against which no antibodies were produced, and compared them to a panel of 950 transplant donors tested in our region, to calculate the probability of a negative crossmatch (PNX). Testing was performed with HLA-coated micro beads to determine PRA and with single-HLA-antigen beads to determine antigens against which no antibodies were produced. Fluorescence results were converted to ESFM, corrected for variable antigen coating of the beads and scored as positive or negative based on a normal serum study. A group of 25 kidney recipients awaiting kidney transplant was chosen for this study. The range of PRA was from 0-100 percent. The sera had 3-13 specific antibodies identified by single-antigen beads and showed high concordance with 35 mismatched HLA-A, B antigens present on previous transplants. A PNX range from 2-85% was observed with little (24%) concordance with the PRA. The PNX was predictive of a negative flow crossmatch in 9/12 (75%) patients while similar concordance occurred in only 4/12 (33%) when PRA was used. If the number of potential donors of a given blood group type is known, it is possible to translate the PNX into an estimate of waiting time. Based on the data obtained, the PNX appears to predict a negative crossmatch more accurately than conventional PRA.