P099 Virtual crossmatching successfully extended donor pool for highly sensitized patients with allele specific antibodies

Abstract

Aim Even with the new Kidney Allocation System, patients with 98–100% cPRA possessing additional allelic antibodies (i.e., the antibody is directed against a polymorphism(s) present in some members of an antigenic group but not others) remain disadvantaged to receive donor organs. Listing the parent antigens as unacceptable (UA) limits an already shallow donor pool. This study presents our experience in expanding the donor pool for this group of patients using a virtual crossmatch (vXM) approach. Methods 38 recipients transplanted with 98–100% cPRA were included. When patients had allele specific antibodies, parent antigens were not considered UA. Instead, when donors possessing parent antigens were offered, a vXM was performed. Donor organs whose allelic specificities were not the targets of the allelic antibodies were transplanted. Patients were followed post-transplant for de novo DSA (dDSA), C4d deposition, acute cellular rejection (ACR), antibody mediated rejection (AMR), and at 1 year creatinine levels ( Results 11 out of 38 (29%) recipients with allele specific antibodies were transplanted with parent antigen positive/allele specificity negative donor kidneys. All vXMs and their corresponding physical crossmatches were negative (Table 1A). The median MFI value for the top strong allelic antibodies was 4013 (range 2314–15603). Transplant outcomes among these patients were compared to the control group of recipients who had no allelic antibodies. Outcomes were identical between the two groups (Table 1B). Conclusions For highly sensitized patients with allele specific antibodies, parent antigens to which patients have allele specific antibodies do not need to be considered as UA. Accurate vXMs can predict donor/recipient compatibility based on allelic DSA. This approach maximizes the donor offers in a timely manner to a particularly disadvantaged group of highly sensitized patients without negative impact to transplant outcomes. Download : Download high-res image (468KB) Download : Download full-size image