15-P

Abstract

Highly sensitized (PRA ⩾ 80%) patients have a significantly reduced probability of finding a matched renal transplant. Newer solid-phase antibody identification assays (Luminex) allow accurate detection and characterization of recipients’ comprehensive anti-HLA antibody profiles. Virtual crossmatching (VXM) utilizes the recipients’ anti-HLA antibody profile and donor’s HLA typing to predict a positive XM. Those antigens that cross-react with high mean fluorescence intensity (MFI) donor-specific antibodies (DSA) are considered unacceptable antigens (UA), a factor used for UNOS calculated PRA (cPRA) formula. As of 2008, all patients on our institution’s deceased donor kidney waitlist have been tested using solid-phase assays. Since 2009, the VXM replaced the prospective preliminary CDC crossmatches. We evaluated the impact of using VXM instead of prospective CDC crossmatches for patient selection in deceased donor renal transplants. For all patients on our institution’s UNOS deceased donor kidney waitlist, a quarterly PRA screening and a yearly single antigen bead (SAB) analysis was performed in sensitized patients. Antibodies with MFI > 3500 were identified as UA’s. A significant change in PRA (>20%) prompted a new SAB analysis. Patients with 1 strong (MFI >5000), more than 2 moderate (MFI = 2001-5000) and 3 weak (MFI = 700-2000) DSA’s were removed from the match run list. All donors were typed for the HLA-A, -B, -C, -DRB1, -DQB1, -DPB1 and DQA1 loci. The transplant rates in highly sensitized patients increased from 0% in 2006 to 14.7% in 2010 (P < 0.05) after the implementation of the VXM in 2009. In addition, the transplant rates for sensitized patients with PRA ⩾20% also increased from 14.3% in 2006 to 20.6% in 2010. For our center, the positive predictive value of the VXM was 80% and 81% for the final T-cell and B-cell FCXM’s, respectively. VCXM resulted in increased deceased donor kidney transplants, particularly in highly sensitized patients.