Experience with the Wujciak-Opelz allocation system in a single center: an increase in HLA-DR mismatching and in early occurring acute rejection episodes

The present single-center, retrospective study was undertaken to assess the impact of the Wujciak-Opelz allocation system (XCOMB), currently used within Eurotransplant for renal allografts, on the incidence of early occurring rejection episodes (RE). Implementation of the system resulted in an increase of HLA-DR mismatches (MM), while the incidence of HLA-A + B + DR MM remained unchanged. During the 1st post-transplant month, the total number of RE, expressed per patient-months, increased by 64 % (0.326 vs 0.199, P = 0.007); when considering only severe and irreversible RE, the increase was 76 % (0.158 vs 0.090, P = 0.011). In contrast, from the 2nd to the 12th post-transplant month, the incidence of RE, regardless of severity, was similar before and after implementation of XCOMB. As early occurring RE have detrimental effects on long-term graft outcome, these observations, if confirmed on a larger scale, would justify changes in the allocation algorithm.