The national policy initiated by the United Network for Organ Sharing (UNOS) in 1987 requires mandatory sharing of all six-antigen-matched kidneys. In 1988, this policy was expanded to include phenotypically identical matches as well. The premise of the policy was that well-matched cadaveric kidneys would have longer graft survival than cadaveric kidneys assigned without regard to match. Proponents concluded that transplantation for all racial and ethnic groups would be minimally affected and that there would be an increase in the number of well-matched grafts compared with poorly matched, locally transplanted kidneys. The purpose of this study was to assess the impact of this policy on one transplant procurement program in Alabama.

Data were compiled on all 33 mandatorily shared cadaveric kidneys and 16 non-six-antigen-matched kidneys shipped to and from the study center. The 33 mandatorily shared kidneys were transplanted into 1 Hispanic (3%), 1 black (3%), and 31 white (94%) recipients. The 16 contralateral kidneys were transplanted into 6 blacks (37%) and 10 whites (63%). All donors were white. PRA values were similar for recipients with mandatorily shared and contralateral kidney transplants, but the number of initial transplants differed between the two groups (73% of the mandatorily shared transplants were the initial transplant, while 94% of the contralateral transplants were initial). There were no significant differences between recipients in the two categories with regard to months on the waiting list, days of hospitalization, serum creatinine concentrations, and the number of rejection episodes. However, those in the mandatorily shared kidney group had a shorter waiting time (average of 12.5 months versus 18.3 months for those with contralateral kidneys) and fewer rejection episodes (27% versus 56% for those with contralateral kidneys). Significantly more of those with mandatorily shared kidneys had dialysis during the first week post-transplant (21% versus none of those with contralateral kidneys). The mean ischemia time was longer for recipients of mandatorily shared (shipped) kidneys.

In the mandatorily shared kidney group, there was no transplant failure in the 24 recipients of primary grafts, and there were two kidneys failures in the 9 re-grafted recipients (from chronic rejection at 16 and 19 months). In the contralateral transplant group, one of the 16 kidneys failed due to accelerated rejection, and two patients died (at 3 days and 3 weeks post-transplant). Survival times ranged from 1 to 27 months for the remaining 13 grafts.

These data show a high success rate of the mandatory sharing program, but evidence of racial disparities was clear. The primary beneficiaries were Caucasians with very common HLA types receiving their first kidney. The primary factor influencing this unequal distribution by race of the mandatorily shared kidneys is difference in HLA type. The small number of blacks benefiting from this policy can be attributed to the majority of the donors being white -
genetic heterogeneity between whites and blacks limits the number of identical matches for blacks from a primarily white donor pool.

The authors state that the improved allograft survival in recipients with mandatorily shared kidneys suggests a need for expansion of the criteria, the impact of which would be an approximately 5-fold increase in the number of kidneys subject to mandatory sharing. This decision may also result in a marginal increase in the number of blacks receiving beneficially matched transplants, as well an improvement in graft survival.