Virtual Crossmatch Predicts Compatibility for Heart Transplantation with Favorable Outcomes in Sensitized Patients

Abstract

Purpose Alloantibodies to human leukocyte antigens (HLA) in patients awaiting orthotopic heart transplantation (OHT) are associated with prolonged wait time to transplant, and increased risk of rejection. Virtual crossmatch (VC) allows comparison of recipient HLA antibodies to prospective donor HLA antigens to safely transplant a patient without prospective crossmatch. We have evaluated the performance at our center, correlating VC results with post-transplant outcomes. Methods and Materials From 2010 to 2012, VC performance was evaluated. HLA antibody testing was performed using Luminex single antigen bead multi-array platforms. Crossmatching was done using 3-color Flow cytometric analysis on a 1024 channel scale. We compared VC with actual crossmatch results, and examined 1-year acute rejection episodes and survival. Results Eighty-four patients were transplanted with a concordance rate of 96.5% between virtual and actual crossmatch results: 79/84 crossmatches were both predicted and confirmed flow crossmatch negative, while 2/84 were predicted and confirmed flow crossmatch positive. One patient with a negative crossmatch demonstrated weak, recently evolved anti-A2 (donor-specific) reactivity by Luminex analysis (MFI=1984) in day of transplant serum. Two patients were predicted to be negative, but positive crossmatches were observed in the absence of detectable donor specific antibodies (possible non-HLA / non-specific fluorescence). A significant number of recipients (28.6%; n=24) were sensitized prior to transplant (3 patients > 80% PRA; 10 between 20-79% PRA; and 11 patients Conclusions Virtual crossmatch accurately predicts actual flow crossmatch results in patients undergoing OHT. This technique can be reliably used in sensitized patients without compromising patient safety or clinical outcome.