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Abstract:
During the 46 years since the first successful kidney was performed, more than 200,000 kidney transplants at United States transplant centers have been reported to the UCLA and UNOS Transplant Registries. After more than 25 years of follow-up, only 4% of cadaver donor transplants and 22% of living donor transplants performed before 1975 are still functioning. When compared with the 30% and 58% 5-year cadaveric and living donor graft survival rates, respectively, reported for kidney transplants 25 years ago, today's results of 66% and 78% are remarkably improved. Between 1995-1999, the 5-year graft survival rates for living donor transplant recipients were 80% for whites, 64% for American blacks and 84% for Asians and others. Among recipients of cadaver kidneys the results for the same racial groups were 70%, 55% and 76%, respectively. HLA-identical sibling transplants provided the best results in whites and blacks with 5-year graft survival rates of 90% and 88% respectively, and superior graft half-lives of 42 and 27 years. No substantial survival differences were noted among whites who received an HLA-mismatched living donor graft (5-year graft survival ranged from 76-81%). Among blacks who received HLA-mismatched living donor kidneys, 69% of sibling grafts survived 5 years compared with 60-62% of all others (p = 0.035). The racial distribution at the 25 largest US transplant centers varied from 6-64% black recipients. Graft survival rates for both blacks and whites were comparable at centers that transplanted more than 33% blacks or less than 20% blacks, suggesting that a larger experience with minority patients does not confer an advantage manifested in graft survival. Blacks consistently had higher rates of early rejection (34% vs. 28% in the first year) and delayed graft function (31% vs. 23%) than whites. Rejection prior to discharge resulted in a decreased one-year graft survival rate from 89% to 76% for both racial groups. DGF also reduced one-year graft survival from 82% to 76% for both racial groups. However, long-term graft survival rates were 15% lower for blacks than whites when there was no rejection or when there was no DGF. Sensitization patterns were similar comparing blacks and whites stratified according to sex, pregnancies, pretransplant transfusions, and previous transplants. There was no indication among patients transplanted between 1995-1999 for higher rates of sensitization among blacks. Recipients over age 60 had the lowest graft survival rate among whites (60% vs. 71% for those aged 19-45; p < 0.001). Among blacks, older recipients had the highest graft survival rate (57% vs. 55% for those aged 19-45; p = ns). Blacks aged 6-18 had the poorest 5-year survival rate (44%). The donor's age was an important determinant of long-term survival in both whites and blacks. The 5-year graft survival rates fell from 74-57% when the donor age was over 60 among whites. However, the difference was more pronounced among blacks, with a 5-year survival rate of 64% when the donor was aged 19-30, 47% when the donor was aged 46-60 and 35% when the donor was over 60 (p < 0.001). Increasing numbers of HLA mismatches resulted in a significantly increased incidence of rejection episodes in both blacks and whites. More than 19% of whites received an HLA-matched graft during 1995-1999 compared with 6% of blacks. HLA matching improved 3-year graft survival by 7-8% for both whites and blacks. Causes of graft failure were similar for blacks and whites during the first posttransplant year, however, after one year, blacks were more likely than whites to have an immunological graft loss whereas whites more often died with a functioning graft. The causes of patient death were also similar between blacks and whites during the first year, but after one year, blacks were more likely than whites to die from infection whereas whites more often died from cardiovascular disease and from malignancies. The racial disparity in renal allograft survival rates has diminished. The graft survival difference between whites and blacks at one year is now less than 2%. The long-term survival rates have also improved for blacks but the rate of late graft loss remains nearly double that for whites.