34-P: THE ACCEPTABLE REACTIVE CROSSMATCH (ARC), POST TRANSPLANT MONITORING AND ITS IMPACT ON KIDNEY TRANSPLANTATION

Aim Multiple clinical studies have shown the adverse effect of HLA antibodies on graft survival, either pre- formed or de novo antibodies post-transplant. The current utilization of more sensitive assays like solid phase assays (SPA) and multiplex techniques, has allowed for the detection of lower levels of HLA antibodies, including donor specific antibodies (DSA) pre and post- transplant. Patients transplanted with low level DSA are considered at higher risk for acute cellular rejection (AR) or antibody mediated rejection (AMR). The aim of our prospective study,looked at low level DSA’s in the context of a negative T and B cell flow cytometry crossmatch or acceptable reactive crossmatch (ARC) and a protocol based post-transplant monitoring graft survival. Methods HLA Class I and II antibody screens and specificities using SPA and a tri color FCXM vs donor and autologous T and B cells were performed. Patients were managed with quadruple therapy including Thymoglobulin ® induction and post HLA antibody monitoring protocol. A negative crossmatch in the presence of low level DSA was not a contraindication for transplant. However, these patients were classified as high risk and followed post-transplant. Results Of 31 ARC patients transplanted, 65% had a PRA >50% and 26% developed an increase in DSA 7-14 days post -transplant. With AMR pharmacological and or PP treatment, DSA were lowered and stayed at low levels (MFI 1000-3000) or below FCXM cutoffs. None of the 31 patients transplanted developed de-novo antibodies. Two patients lost their grafts, one to BK and one to AMR. Conclusions Our experience demonstrates that patients deemed higher risk for an immunological event due to low level DSA should be transplanted with an ARC and followed post-transplant according to an established protocol. With close monitoring, 5 year outcomes can be expected to approach that of low immunologic risk groups.