P027 : DONOR SPECIFIC HLA ANTIBODIES DETECTED BY LUMINEX CANNOT PREDICT THE OUTCOME OF A CDC OR FLOW CYTOMETRIC CROSSMATCH IN AN INDIVIDUAL PATIENT

Abstract

For clinical purposes it is necessary that before a renal transplantation takes place, the patient is screened for the presence of circulating HLA antibodies that may harm the transplanted kidney. Antibody analysis is nowadays often performed by testing the reactivity towards HLA molecules bound to Luminex beads. The prospective crossmatch, however, is performed either by the complement-dependent cytotoxicity assay (CDC) or by flow cytometric assays. In the current study we compared the outcome of the luminex single antigen (SA) analysis with respect to the presence of donor specific antibodies (DSA) and the crossmatch result of 125 patients. CDC crossmatch results (pos/neg) and flow cytometric T cell and B cell crossmatch results (mean channel shift) were related to anti-class I or anti-class II reactivity in luminex (MFI). Results On the population level, there was a significant association between the sum of the MFI’s of the donor reactive HLA class I and II antibodies and outcome of the CDC cross match. However, when the significance for individual patients was analysed, the situation is less clear. Numerous negative CDC crossmatches were observed in case of high DSA levels in luminex ( Fig. A ). With respect to the flow T cell crossmatch, a higher channel shift was observed when anti-donor luminex reactivity increased but, in general, the correlation was poor. Similar findings were observed for the flow B cell crossmatch ( Fig. B ). In conclusion, despite the presence of a clear correlation between DSA detected by Luminex and the crossmatch result on the population level, for an individual patient one cannot rely on measurement of DSA by luminex only. This observation is very important if one considers the introduction of a virtual crossmatch. A combination of techniques will be necessary in order to predict in a reliable way the outcome of a crossmatch in sensitized individuals.