Importance of HLA antigen splits for kidney transplant matching.

Whether matching for HLA antigen "splits" results in better transplant outcome than matching for "broad" HLA antigens was investigated in 30,000 first cadaver kidney transplants. At three years, there was an 18% difference between the survival rates of grafts with 0 or 4 mismatches among transplants typed for HLA-A and B antigen splits whereas the difference in transplants typed for broad antigens was only 2%. Analysis of HLA-A, B antigens together with HLA-DR antigens showed an even greater advantage of matching for antigen splits: the difference in survival at three years between grafts with 0 or 6 mismatches for HLA-A, B, DR was 31% when antigen splits were analysed, in contrast to a 6% difference with broad antigens. These results indicate that typing for HLA antigen splits is important in renal transplantation, that the potential benefit of HLA matching in renal transplantation is greater than currently accepted, and that HLA typing and kidney allocation routines must be refined in order to exploit this potential.