Date: Sunday, April 30, 2017
Session Time: 2:30pm-4:00pm
Presentation Time: 3:06pm-3:18pm
Purpose: Virtual crossmatch (VXM) has been utilized in heart transplant (txp) for more than a decade. Many labs base the VXM solely on single antigen bead (SAB) results; however SAB assays are prone to false negative (FN) results due to prozone-like effects from endogenous complement or antibody (Ab) against public or shared epitopes. False positive (FP) results due to reactivity with cryptic epitopes on denatured HLA antigens (Ags) are also common. Therefore to avoid erroneous VXM interpretation, it is critical to inactivate complement prior to testing and to use multiple solid phase immunoassay (SPI) platforms.
Methods: We retrospectively studied 45 consecutive heart txps. In order to define unacceptable Ags for VXM, patients (pts) were tested using Flow PRA Screen, LabScreen PRA (LSPRA) and SAB (One Lambda Inc). All sera were pre-treated with EDTA to inactivate complement in order to avoid FN reactions. FP reactions were ruled out through analysis of parallel SAB and phenotype-based LSPRA assays. All sera were evaluated for the presence of Ab to shared epitopes. Potential Ab to shared epitopes was identified through comparison of flow PRA Screen and SAB results. When discrepancies were identified, epitope analyses were performed using the HLA Epitope Registry. A positive VXM was defined as the presence of donor specific Ab.
Results: 45 pts were studied, 17 (38%) were HLA Ab positive, 10 (22%) had FP Ab. Of the pts with Ab, 6 (35%) had reactivity with a public or shared epitope. Our flow crossmatch (FXM) results showed 100% correlation with VXM.Conclusion: Accurate VXM can only be achieved using multiple SPI platforms. If Ab assignment is based solely on SAB results from untreated sera, unpredicted positive FXMs will be encountered and a significant number of pts could be inappropriately denied txp due to FP Ab assignments. In addition, use of multiple SPI platforms can be critical to recognize the presence, and assess the strength, of Ab against shared epitopes.
CITATION INFORMATION: Li D, Timofeeva O, Awwad M, Cody C, Najjar S, Rosen-Bronson S. Precise Antibody Characterization Using Multiple Solid Phase Assay Platforms Is Critical for Accurate Virtual Crossmatching. Am J Transplant. 2017;17 (suppl 3).
To cite this abstract in AMA style:Li D, Timofeeva O, Awwad M, Cody C, Najjar S, Rosen-Bronson S. Precise Antibody Characterization Using Multiple Solid Phase Assay Platforms Is Critical for Accurate Virtual Crossmatching. [abstract]. Am J Transplant. 2017; 17 (suppl 3). https://atcmeetingabstracts.com/abstract/precise-antibody-characterization-using-multiple-solid-phase-assay-platforms-is-critical-for-accurate-virtual-crossmatching/. Accessed December 9, 2019.
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