OR10: SUCCESSFUL USE OF VIRTUAL CROSSMATCH (VXM) IN DECEASED-DONOR RENAL TRANSPLANTATION (DDRT): A SINGLE CENTER EXPERIENCE

Abstract

Aim To evaluate safety and efficacy of VXM in DDRT. Methods Quarterly sera from patients actively waiting for DD were tested for HLA antibodies using single antigen bead method. Targets of class I (>2000 MFI) and class II (>1000 MFI) antibodies were listed as unacceptable HLA in UNet, and thus the VXM is predicted to be negative with any offered donor. Based on negative VXM, 56 candidates received HLA mismatched transplants (52 kidney alone; 4 combined pancreas-kidney) at UCSF Medical Center between 11/ 2012 and 7/2013. Donor-specific T and B cell flow cytometric crossmatch (FCXM) was performed retrospectively, and results were not revealed to the treating physicians and thus did not influence the choice of immunosuppression (IS). Recipient data: Mean(SD) age was 52.5(14) years; 30% were female; 2 were re-transplant candidates. 17 (31%) recipients had no HLA antibodies, while 16 (29%) had 2–19% CPRA, 7 (12%) had 20–39% CPRA, 6 (11%) had 40–60% CPRA, and 10 (17%) had DP/Cw antibodies. Race distribution: 30% Hispanics, 25% African-Americans, 25% Caucasians, and 17% Asian. Causes of ESRD were Diabetes (30%), Glomerular diseases (28%) and Hypertension (12%). Induction IS included ATG (54%) and simulect (46%). Maintenance IS included MMF (100%), tacrolimus (94%) and prednisone (75%). Donor data: Mean(SD) age and cold ischemia time were 36.2(13.8) years and 11.4(4.8) hours respectively. Donor types: standard criteria (71%), donation after cardiac death (17%) and extended criteria (9%). Results As we predicted, nearly all (55/56; 1/56-false positive) FCXM were negative. Six-month patient and graft survivals were 100% and 96% respectively (n = 50). Mean(SD) serum creatinine at month 6 and month 9 ( n = 19) was 1.23(0.46) mg/dl (93.79 + 35 mmol/l) and 1.15(0.32) mg/dl (87.69 + 24 mmol/l) respectively. Seven patients (12.5%) experienced 8 episodes of acute rejections (4 each on protocol and cause biopsies), none of which resulted in allograft loss. 50% of rejections were borderline, 38% ( n = 3) as ACR type 1a and 12% ( n = 1) as acute AMR. Conclusion VXM correctly predicts the results of FCXM in an ethnically diverse, low-moderate immunologic risk recipient population. Use of VXM does not increase the rate of early allograft rejection. VXM can eliminate physical crossmatch test and therefore minimize cold-ischemia time in DDRT.