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THE DISADVANTAGE OF BEING AN HLA HOMOZYGOUS KIDNEY PATIENT: LONGER WAITING TIME, MORE MISMATCHES AND POORER GRAFT SURVIVAL.
Ilias Doxiadis 1,2, Geert Haasnoot 1, Guido Persijn 3 and Frans Claas 1,2. 1 Immunohaematology and Blood Transfusion, LUMC, Leiden, Netherlands ; 2 Eurotransplant Reference Laboratoy, LUMC, Leiden, Netherlands and 3 Eurotransplant International Foundation, Leiden, Netherlands .
Organ allocation organizations have been established to achieve an optimal degree of histocompatibility between organ donor and recipient leading to an increase in graft survival. However, a well-matched graft is difficult to achieve in patients that are homozygous for the HLA antigens. We investigated the effect of homozygosity on the waiting time, degree of histocompatibility and graft outcome. We analyzed 14,322 transplants performed from 1996 
2004, the period of the new Eurotransplant Kidney Allocation System, and applied a multiple linear regression for the analysis. Homozygous patients and in particular HLA homozygous female patients, have a significantly higher level of current and highest panel reactive antibody value (p<0.001 and p<0.0005), wait significantly longer for a suitable crossmatch negative organ (p<0.0001), receive on average a graft with more HLA mismatches and have a significantly reduced two years graft survival (p<0.05) compared to heterozygous patients. In the current allocation system organs from HLA, homozygous donors are often preferentially allocated to heterozygous recipients. In order to enhance transplantation of homozygous recipients, organs from homozygous donors should be preferentially allocated to HLA matched homozygous recipients.