IDENTIFICATION OF UNACCEPTABLE ANTIGENS USING FLOW CYTOMETRIC BEAD TECHNIQUES TO SIGNIFICANTLY REDUCE UNNECESSARY CROSSMATCHES FOR SENSITIVE PATIENTS.

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IDENTIFICATION OF UNACCEPTABLE ANTIGENS USING FLOW CYTOMETRIC BEAD TECHNIQUES TO SIGNIFICANTLY REDUCE UNNECESSARY CROSSMATCHES FOR SENSITIVE PATIENTS.
Walter F. Herczyk , Barbara O. Burgess , Janet Tuttle-Newhall and Nancy L. Reinsmoen . Durham NC, Duke Univ. Med. Ctr., Clin. Transplt. Immunol. Lab, 27710, Pathology .

Sensitized patients, (PRA >45%) awaiting solid organ transplants are usually crossmatch positive due to the difficulty in identifying antibody specificity. The crossmatching of these patients that result in a positive crossmatch are often unnecessary and time consuming. Single antigen beads and LUMINEX methodology were used to determine antibody specificity (One Lamda, Inc) for these solid organ patients. To see if the antibody identification accurately predicted the crossmatch outcome, we analyzed the results for 24 sensitized patients called in for crossmatching. Of the 24 patients, 13 had PRAs >80% and 11 had PRAs >45% (anti-Class I and/or II). A total of 38 donor specimens were tested by CDC-AHG and/or flow cytometry crossmatches. The unacceptable antigen analysis accurately predicted 25 positive crossmatches and 13 negative crossmatches (100% concordance). Based on these results, we used the unacceptable antigens defined to select patients for final crossmatches. The positive crossmatch rate decreased from 33% (2001) to 25% (2002) to 10% (2003). Considering that 30% of our transplanted recipients had PRA >20% compared to the national average of 11.20% (p=0.00.1), identification of unacceptable antigens has reduced the overall crossmatch rate by 41% while allowing for a significantly higher percentage of sensitized patients to be transplanted locally than the national average. An accurate assessment of unacceptable antigens for these patients, and utilization of this information to determine crossmatch pairs has decreased the cost for crossmatching, facilitated a more rapid organ allocation, and decreased the time and cost associated with patients traveling to the transplant center unnecessarily.