Survival of mandatorily shared cadaveric kidneys and their paybacks in the zero mismatch era

Background. The United Network for Organ Sharing has mandated the national sharing of well-matched cadaveric kidneys with payback to the national pool. On March 6, 1995, the policy was extended to include sharing of cadaveric kidneys for which there is a recipient with a 0-HLA mismatch (0-MM). However, the beneficial effects of this policy have been questioned. To address these concerns, we analyzed the effects of this system on graft survival, cold ischemia time, and the transplantation of highly sensitized patients during the 0-MM era. Methods. We analyzed cadaveric solitary kidney transplant data in the OPTN/The United Network for Organ Sharing database. Cox proportional hazards analyses were conducted on 29,401 transplants performed between March 6, 1995 and December 31, 1998 to assess the effects of mandatory sharing and paybacks on graft outcome. We also compared the outcome of pairs of kidneys in which one was shared as either an 0-MM kidney (n=833) or as a payback (n=440) and the mate was transplanted locally. Results. Overall, 36% of kidneys were shared, 15.6% as 0-MM and 20.4% as paybacks or other shares. Although the sharing of 0-MM kidneys significantly increased cold ischemia time, the risk of graft loss was significantly decreased. The survival of payback kidneys was not significantly different from other shared kidneys. Sharing 0-MM kidneys appeared to increase the chances of transplantation of sensitized patients and 47% of the kidneys transplanted in patients with a panel reactive antibody of more than 80% were from 0-MM donors. Conclusions. National sharing of 0-MM kidneys appears to lead to a small but significant improvement in intermediate-term graft survival despite increasing cold ischemia time. The current policy also increases access of highly sensitized patients to transplantation.