Relative Importance of HLA Mismatch and Donor Age to Graft Survival in Young Kidney Transplant Recipients

Abstract

The American deceased-donor (DD) kidney allocation algorithm for children emphasizes the importance of younger donors and shorter waiting times over human leukocyte antigen (HLA) matching. We sought to compare the relative importance of donor age with that of HLA mismatching (MM) on graft survival. We studied patients less than 21 years old recorded in the U.S. Renal Data System, who received a first transplant from a DD 5 years old or younger or from a living donor (LD). Using separate Cox proportional hazards models for DD and LD recipients, we estimated the adjusted 5-year probability of graft survival for each donor age-HLA MM combination and compared estimated graft survival across the different HLA MM-donor age combinations. Both donor age and HLA MM were significantly associated with DD graft survival, whereas only HLA MM had a significant association with LD graft survival. Compared with DD grafts from less than 35-year-old 4-6 MM donors, survival was not significantly different for 0-1 and 2-3 MM grafts from 35- to 44-year-old donors or for 0-1 MM grafts from donors 45 years old or older. The most poorly matched grafts from the oldest LD had survival similar to or better than any DD. Donor age and HLA MM both play important roles in determining DD graft survival. The advantages of younger donors offset the disadvantages of poorer HLA matching, and better HLA matching offsets the disadvantages of older donor age.