Evaluation of Hla Matching for Creg Antigens in Europe1

BACKGROUND: In North America, cross-reactive antigen group (CREG) matching was introduced recently for cadaver kidney allocation. This is expected to result in improved graft outcome and an increased number of transplants for patients with rare HLA antigens. METHODS: We analyzed the impact of CREG matching using the data of the Collaborative Transplant Study for 59,516 first cadaver transplants performed in Western Europe. The 10 HLA class I CREGs described by Takemoto et al. were used for a comparison with the conventional HLA-A+B mismatching scheme. RESULTS: Transplant outcome depends primarily on the number of HLA-A+B mismatches and not on the CREG match grades. In a retrospective analysis, CREG mismatches correlated with the number of HLA-A+B mismatches. However, in computer simulations, we found that prospective CREG matching is not associated with beneficial HLA-A+B matching. CONCLUSION: The positive CREG matching effect observed in retrospective analyses is caused by the underlying effects of conventional HLA-A+B matching. CREG-oriented cadaver kidney allocation in Europe would, therefore, be inferior to the current conventional HLA-A+B+DR allocation.