Significant Increase in Cadaveric Renal Transplants in Highly Sensitized Patients by Implementing Virtual Crossmatch: A Unicenter Experience
Sangeeta Mehendale, Bozena Labuda, Andres Jaramillo, Sujata Gaitonde. University of Illinois at Chicago, Chicago, IL; Histocompatibility Laboratory, Gift of Hope Organ & Tissue Donor Network, Itasca, IL
Background: Highly sensitized patients (PRA: panel reactive antibodies ≥80%) 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 cross matching (VCXM) utilizes the recipients' anti-HLA antibody profile and donor's HLA typing to predict a positive cross-match with greater accuracy and predictability. Those antigens that cross-react with the recipients' serum with a high mean fluorescence intensity (>2000) are considered “unacceptable antigens”or UA, a factor used for UNOS calculated PRA (cPRA) formula. VCXM also permits quicker organ allocation, reducing cold ischemia time and provides important risk assessment. As of 2008, all patients on our institution's cadaveric renal wait-list have been tested using solid-phase assay. Since 2009, VCXM replaced the prospective preliminary complement dependent cytotoxicity (CDC) cross-match to predict a positive final cross-match. We evaluated the impact of using VCXM instead of prospective CDC cross matches for patient selection for final flow cross-matches in cadaveric renal transplants.
Design: For all patients on our institution's UNOS cadaveric renal wait list, a quarterly PRA screening and a yearly single antigen bead (SAB) analysis was performed in sensitized patients. A significant change in PRA (>20%) prompted a new SAB analysis and updating their UAs in the UNOS database. Patients with more than 2 moderate, 3 weak, or 3 undetermined strength current (18 months) donor-specific antibodies (DSA) were removed from the match run list. All donors were typed by molecular HLA-A, -B, -Cw, -DR, -DQ and -DP typing.
Results: The transplant rates in highly sensitized patients increased from 0.0% in 2006 to 14.7% in 2010 (almost 15 fold increase, p<0.05) after the implementation of the VCXM in 2009, prior to which, prospective CDC cross-matches were used to select recipients. 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 VCXM was 80 % and 81% for the final T-cell and B-cell flow cytometric crossmatch, respectively.
Conclusions: Virtual crossmatching resulted in increased cadaveric renal transplants, particularly in highly sensitized patients.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 214, Wednesday Morning