Daniela Bau, Gary Sawers, Anja Wahle, Wolfgang Altermann and Gerald Schlaf
Antibodies directed against HLA antigens of a given donor represent the most prominent cause for hyper-acute and acute rejections. In order to select recipients without donor-specific antibodies the complement-dependent cytotoxicity (CDC-) crossmatch was first established representing the standard procedure up to the present. Its negative pre-transplant outcome is currently regarded as the most important requirement for a successful short term kidney graft survival. As a functional assay, however, it strongly depends on the availability of isolated donor lymphocytes and in particular on their vitality. Moreover, during the last ten years several disadvantages of the CDCbased procedure have increasingly been discussed with respect to this assay’s high susceptibility to disruptive factors which frequently lead to false positive outcomes. In this context several autoimmune diseases especially of the immune complex type (type III) or pharmacological treatment of a given recipient have been shown to lead to unexpected “false-positive” outcomes of the CDC-crossmatch. As methodical alternatives for anti-HLA antibody specific cross-matching two ELISA-based procedures i) the Antibody Monitoring System (AMS-) ELISA and ii) the AbCross-ELISA were established in our tissue typing laboratory and those of some other groups. Both systems, however, were discontinued for mere commercial reasons in the years 2013 and 2016, respectively. Using the same set of diagnostic antibodies, the AMS-ELISA, now named Donor-Specific Antibodies/DSA, was afterwards again manufactured as a microbead-based array using the Luminex platform. With a view to establish the DSA-assay as the only remaining solid phase-based crossmatch system commercially available, this procedure was systematically evaluated in our laboratory. Primarily but not exclusively based on drawbacks of the evaluation software, however, 69 (32.5%) of the virtually defined crossmatch results (n=212 independent anti-HLA class I and II specifications and their corresponding DSA-assays, respectively) were classified as divergent using the DSA-assay whereas only 143 results (67.5%) were classified as accordant by this assay’s software. Referring to the chosen cohort of recipients (n=106) not less than 62 (58.4%) of them are characterized by findings which are not supported by virtual crossmatching. We here provide evidence that for various reasons the outcomes provided by the DSA-assay, in contrast to those of the AMS-ELISA as its precursor system, have critically to be challenged. We therefore conclude that modifications are urgently required to be introduced by the manufacturer in order to lead again to a system of sufficient validity usable for any laboratory’s routine diagnostics.