73 Luminex detected antibodies are clinically relevant in pretransplant risk assessment

73 Luminex detected antibodies are clinically relevant in pretransplant risk assessment Veskimäe P.1, Vassil L.2, Kotsar A.1, Kirsimägi U.1, Kahu J.1 1 Tartu University Hospital, Dept. of Urology and Renal Transplantation, Tartu, Estonia, 2Tartu University Hospital, United Laboratories, Dept. of Immunoanalysis, Tartu, Estonia INTRODUCTION & OBJECTIVES: Complement-dependent cytotoxicity (CDC) crossmatch has been used almost 50 years in kidney transplantation to assess the presence of preformed donor-specific antibodies (DSA). Last years more sensitive solid-phase assays, such as Luminex, have been increasingly used in organ transplantation. However, the clinical relevance of antibodies (Ab) detected only by Luminex remains unclear. MATERIAL & METHODS: Our standard policy has been to screen kidney transplant waiting list quarterly with ELISA and CDC methods. Since 2012 Luminex xMAP technology has been implemented in our centre. Each patient on a waiting list is tested by Luminex Single Antigen twice a year, MFI cut-off 1000 is generally used. We aimed to assess impact of Luminex detected HLA Ab and DSA on early acute rejection (AR) rate compared with ELISA and CDC methods. 130 patients were transplanted after the introduction of Luminex assay during the period of 2012-2014. 2 patients were excluded because of liver-kidney combined transplantation. RESULTS: 107 were first and 21 re-transplantations. 13% had cytotoxic HLA antibodies, ELISA class I was positive in 38%, ELISA class II in 30% of patients. Luminex Single Antigen analysis was positive in 57 (45%) recipients, 24 (19%) of them had donor-specific antibodies (DSA). All patients were CDC crossmatch negative in transplantation. In overall 27% of patients had biopsy proven AR during first 6 months after transplantation. Higher PRA level, positive ELISA I and ELISA II tests did not predict AR rate after kidney transplantation. From baseline parameters only HLA match was associated with AR rate. There were significantly more rejections in patients with Luminex detected HLA Ab (33% AR), in particular with DSA (50% AR), compared to HLA Ab negative (23% AR) and DSA negative (22% AR) groups. Both humoral and overall AR rate correlated with presensitization level (the amount of different HLA Ab). CONCLUSIONS: Luminex assay adds predictive value to older screening methods (CDC and ELISA) to determine patients with higher AR risk. We need to adapt our treatment strategy in the presence of DSA in Luminex assay: protocol biopsies, desensitization or increased immunosuppression in induction/maintenance regimens. Eur Urol Suppl 2015; 14(3): e1167