P122 Virtual crossmatch to assist with timely evaluation of donor compatibility for sensitized national kidney registry recipients

Abstract

Aim The National Kidney Registry (NKR) has reduced wait time for patients with incompatible donors. Utilizing Virtual crossmatch (vXM) to predict viable NKR donors with sensitized NKR recipients can expedite exploratory crossmatch (EXM) orders and place recipients in a chain swap sooner. Evaluating weak DSA will help clarify the need for an EXM or declining the donor. Methods vXM was done using patient HLA-Ab information and donor allelic level DSA. HLA-Ab assignment was performed by Luminex single antigen beads using EDTA treated patient serum. If clarification was needed, Phenotyping beads and/or Flow Single Antigen beads were tested. A vXM was done to evaluate need for an EXM to prevent swap failures and/or include recipients in a chain swap. EXM were executed using cryo-preserved cells. Due to limited cell yield only flow XM were done for EXM. Final XM were performed using T and B CDC and flow XM. Results At the Cleveland Clinic, cutoff for HLA-Ab reported to the NKR is > 4000 Mean Fluorescence Intensity (MFI). Seventy vXM were performed between January 2016 and March 2017. Twenty-eight vXM had weak (MFI = 1000–3999 MFI) DSA. EXM’s were suggested when weak DSA was observed in the vXM or for highly sensitized patients. Results of twenty-two EXM/screening XM (screening XM were the result of donor preselects) that were ordered showed seventeen cases had single DSA (CI = 9 CII = 8). These were predicted by vXM to be negative. This was 100% concordant to the EXM and final XM (Table 1A). Five cases had multiple DSA (CI = 2, CII = 2, CI & CII = 1), all predicted by vXM to be negative to weak positive. This was 100% concordant to the EXM and final XM (Table 1B). Conclusions vXM based on number and intensity of DSA was 100% concordant with EXM and Final XM. This assists in reliable donor selection for NKR recipients. vXM provides a quick evaluation of NKR donors for highly sensitized patients or patients with weak DSA. Reporting EXM quickly to the NKR reduces wait time and enables NKR recipients to become part of a successful chain swap. Download : Download high-res image (247KB) Download : Download full-size image