AN ANALYSIS OF DISCREPANCIES IN HLA PHENOTYPES OF CADAVER DONORS IN THE UNITED-NETWORK-FOR-ORGAN-SHARING-REGISTRY

Background. HLA matching is an important component of the United Netwo rk for Organ Sharing algorithm for kidney allocation and is the primar y factor in the mandatory sharing of kidneys that have zero HLA antige ns mismatched with specific patients on the waiting list, An assessmen t of the HLA-A, -B, and -DR antigen discrepancy rate in the Organ Proc urement and Transplantation Network database is desirable to judge the adequacy of the HLA typing data upon which the allocation program is based, Methods. A subset of the Organ Procurement and Transplantation Network. database, composed of 10,047 cadaver donor HLA phenotypes tha t have been repeated by laboratories affiliated with organ recipient c enters, was analyzed for the overall rate of HLA phenotype discrepancy and for the type and frequency of discrepancies of the individual HLA antigen assignments. The United Network for Organ Sharing HLA antigen equivalences were applied to the data. Results. Fourteen percent of 1 2,419 HLA typing comparisons were discrepant in at least one HLA antig en of six possible antigens per phenotype, Of a possible 74,514 indivi dual HLA antigen assignments, 2.7% were discrepant. For African-Americ an donors, the discrepancy rate was 5.1% as compared with 2.4% for Cau casian donors. The most frequent type of discrepancy was the assignmen t of an antigen blank versus a named antigen. Conclusions. The discrep ancy rate is comparatively low and can be expected to improve as more laboratories adopt methods for HLA typing by DNA typing techniques, It is recommended that the HLA data be further reviewed by the laborator ies for possible typographical errors and that centers review the UNOS listing of HLA antigen equivalences and encourage laboratories to spl it HLA antigens.