#6257 PROGNOSTIC VALUE OF A POSITIVE CROSSMATCH BEFORE DESENSITIZATION IN A COHORT OF HIGHLY-SENSITIZED PATIENTS

Abstract Background and Aims Human Leukocyte antigen (HLA) sensitization in patients is a barrier for Kidney Transplantation (KT) access, and highly-sensitized patients remain on the waiting list longer than other patients which results in a higher morbidity and mortality. Desensitization may be an option to increase their access to KT. All patients transplanted in this context have a negative Complement-Dependent Cytotoxicity crossmatch (CDC-CM) the day of KT. However, the stratification of the long-term risk of graft loss according to flow cytometry crossmatch (FC-CM) and to CDC-CM during the desensitization period remains unknown. Method In this retrospective study, all highly-sensitized patients (Panel Reactive Antigen (PRA) ≥ 85) in our center were included. CDC-CM and FC-CM were performed on samples before and during the desensitization period and clinical follow-up data were retrieved. Pre-KT desensitization strategy consisted in two Rituximab infusions (375mg/m2) and a variable number of apheresis (mostly semi-specific immunoadsorption) associated with a classical immunosuppression-based regimen (tacrolimus, mycophenolate and steroids). Results A total of 183 highly-sensitized recipients received a KT between 2014 and 2022. Of these, 23 were desensitized prior to KT and among them 18 had a positive FC-CM before KT and 5 had no positive FC-CM on all assessed serums. Mean age was 52.9 ± 13 years. Mean follow-up was 5.2±4 and 3±2 years for non-desensitized and desensitized patients respectively. PRA before desensitization was higher in desensitized patients (98%) versus non-desensitized patients (95%) and the mean time on the waiting list was 5.8±4 versus 7.5±4 years respectively. Death-censored graft survival and patient's raw survival, using cox-survival analysis, were not statistically different between the desensitized kidney transplanted patients and the highly-sensitized patients without desensitization (p = 0.77 and p = 0.57 respectively). In sub-group analyses, the positivity of FC and/or CDC-CM did not add an additional risk of graft loss or patient mortality. Conclusion Desensitization allows highly-sensitized patients to access KT with an HLA-incompatible graft (with a positive CDC or FC-CM on the serum collected prior to desensitization), with the same graft survival as similarly sensitized patients transplanted with an HLA-compatible graft without desensitization.