The new Eurotransplant kidney allocation system: a justified balance between equity and utility?

Abstract

Sir: We have read with interest the article `Experience with the Wujciak-Opelz allocation system in a single center: an increase in HLADR mismatching and in early occurring acute rejection episodes' by the renal transplant program Brussels ± Erasme [6]. The authors reported that they experienced a greater number of, and also more severe, rejection episodes during the first post-transplant month under the new Eurotransplant (ET) kidney allocation system [4] than under the old one. HLA-DR mismatches were also found to be more numerous with respect to the new system. It is indeed true that the new kidney allocation system has redistributed the number of HLA-DR mismatches (cf. [6], Table 1); this was mainly a shift from zero HLA-DR mismatches (63 %) to one HLA-DR mismatch (50 %), though without changing the overall HLA-A,B,DR mismatch distribution significantly [1]. Unfortunately, the authors fail to demonstrate the direct link between the HLA-DR mismatch redistribution and their higher incidence of early occurring rejection episodes. They only logically establish an association of the two phenomena. A two-by-two table of incidence of rejection in relation to HLA-DR mismatch is missing. We do not negate the beneficial effect of HLA-DR matching during the first post-transplantmonths, even when the end point is `rejection' instead of the more common end point `graft survival'. It should,however,be added that there is often no distinction between the graft survival of renal transplants with no and those with one HLA-DR mismatch [3]. This finding, in addition to data from the CTS study, supported the notion that less attention could be paid to HLADR mismatching under the new ET kidney allocation system, while aiming at maintaining or even improving the overall HLA-A,B,DR match; in the simulation studies, the latter parameter was used as a surrogate for graft outcome at one year after transplantation [7]. The authors have regularly advocated the concept of `nonimmunogenic' HLA-DR mismatches [5]. It is true that they had more opportunity to select transplant candidates with `nonimmunogenic' HLA-DR mismatches under the previous ET allocation system. It would therefore be interesting to know whether there was a higher percentage of `immunogenic' HLA-DR mismatches under the new ET system, and its relation with rejection incidence. If there was, this might greatly support the authors concept and, indeed, might lead to a re-consideration of HLA-matching policies, as proposed by them [2]. Focussing criticism of the new ET kidney allocation system on the poorer HLA-DR matching seems to be unjustified. The new ET kidney allocation system is able to offset the disadvantages of the previous `exclusively HLA-driven' system [1], namely: