28-P

Abstract

Aim Virtual cross matches (VXMs) are key to the success of KPD by aiding identification of compatible donors for sensitized candidates. We evaluated the success of unstandardized VXMs combined with donor preselection by National Kidney Registry (NKR) centers in a population of mostly sensitized and/or ABO incompatible patients. Methods The NKR initiated 437 match offers among 62 US transplant centers based on acceptable VXMs between 3/14/2011 to 3/31/2012. We evaluated the accuracy of the VXM by examining whether or not offers were declined due to positive final XMs. The VXM considered antibodies to HLA-A, B, C, DRB1/3/4/5, DQB1 and DPB1 detected by Single Antigen assays and donor HLA typing. Each center established its own immunological criteria for donor acceptability. To reduce late stage match failures online pre-selection of donors was introduced in July 2011 which allowed centers to accept potential donors based on HLA types and other characteristics prior to a match run. Results NKR centers achieved a 92% VXM accuracy rate and completed 181 transplants; 32% of these had PRA > 80%. Only 29 (8%) offers were rejected by the recipients’ center due to an unacceptable positive final crossmatch. In most cases, the discrepancy with the VXM was due to DSA at or near the center’s threshold or to multiple DSAs when each fell below the threshold of unacceptability. Other cases were due to DQA antibodies (3), non-HLA antibodies (3), a change in antibody profile (1), and data entry error (1). Interestingly, the rate of false negative VXM remained unchanged after the implementation of the pre-selection strategy, while the rate of late-stage cancellations due to unacceptable donors decreased from 5% to 2%. Conclusions Access to transplant for sensitized patients with minimal disruption of chains has improved by pre-selection of acceptable pairs, optimizing data entry for the VXM, frequent antibody monitoring following sensitizing events and good communication between transplant centers and their labs. Sinacore: NKR: Employee.