Racial differences in the survival of cadaveric renal allografts. Overriding effects of HLA matching and socioeconomic factors.

BACKGROUND: The long-term survival of cadaveric renal allografts is lower in black recipients than in white recipients, although the one-year graft survival is similar in these racial groups. We sought to determine what factors account for this disparity.
METHODS: We studied 100 consecutive recipients of primary cadaveric renal allografts (57 were black and 43 white) at least 1 year after transplantation (mean, 40 months); all had received identical immunosuppressive therapy. We evaluated differences in the cause and duration of end-stage renal disease, the number of pretransplantation transfusions, age, matching for HLA-A, B, and DR antigens, race of the donor, insurance coverage, and compliance to assess their effect on graft survival in both groups.
RESULTS: Allograft survival after one year was significantly lower in black than in white patients (P = 0.025). According to univariate analysis, only the recipient's age at transplantation, the number of mismatches for HLA antigens, the type of insurance coverage, the source of referral for transplantation, and the degree of compliance correlated significantly with the rate of graft survival. The frequency of all variables that reduced graft survival was higher among the blacks. According to proportional-hazards analysis, the only factors contributing to a lower rate of graft survival were age of less than 30 years at transplantation (relative risk, 2.3; 95 percent confidence interval, 1.3 to 4.6), mismatches for all six HLA antigens as compared with three or fewer mismatches (relative risk, 5.6; 95 percent confidence interval, 3.3 to 9.6), and coverage by Medicaid or Medicare (relative risk, 2.2; 95 percent confidence interval, 1.5 to 3.2). Race had no additional effect. Noncompliance was more frequent among blacks (16 percent vs. 2 percent) and could substitute for insurance status in the model.
CONCLUSIONS: When immunosuppression is equivalent in black and white transplant recipients, apparently race-related differences in the long-term survival of renal cadaveric allografts appear to be related to other factors that affect graft survival unfavorably, notably poor HLA matching and unfavorable socioeconomic factors.