THE DISTRIBUTION OF HLA ANTIGENS AND PHENOTYPES AMONG DONORS AND PATIENTS IN THE UNOS REGISTRY

We have analyzed HLA data from the UNOS registry on 20,230 patients o n the renal waiting list in 1991 and 18,708 donors from 1988-1992. Sig nificant differences were found in the distribution of HLA antigens fo r comparisons of the total donor pool and the various racial groups of patients as well as for inter- and intraracial comparisons of donors and patients. Within a racial group, the frequencies of blanks and of broad antigens were usually higher in patients while those of splits w ere usually higher in donors. Comparisons between the total donor pool and the various racial groups of patients showed that the likelihood of mismatch was greater for African-Americans and Hispanics than for C aucasians but that the chance of mismatch is high for all groups and t he average number of antigens mismatched will not vary greatly among t he different races. Heterogeneity, as measured by the percentage of th e population with different phenotypes, was higher in African-American s (97.2-99.1%) and Hispanics (97.7-99.4%) than in Caucasians (83.3-86. 5%) because of multiple occurrences of a few phenotypes, most containi ng A1, B8 and DR3, in Caucasians. However, the most common phenotypes of Caucasian donors differed from those of Caucasian patients. Ah phen otypes were rare (0.007-0.61%) and, with the exception of a small grou p of Caucasian patients, the likelihood of achieving a good match is l ow, regardless of race. These data explain the observations that, with the exception of the phenotypically identical match, HLA matching doe s not influence organ distribution significantly.