Comparison of two Luminex Single-Antigen bead flow cytometry assays for detection of Donor Specific Antibodies after renal transplantation

Background Defining the clinical relevance of Donor Specific HLA antibodies (DSA) detection by Luminex Single Antigen (LSA) flow beads assay is critical in monitoring posttransplant outcome. Methods Sera of kidney transplanted patients were tested by LSA1 and LSA2 with One Lambda Labscreen (test 1) and Immucor Lifecodes (test 2), at the time of a graft biopsy. The first group (G1, n=50) had a biopsy highly suggestive of humoral rejection and the second (G2, n=50) had no criteria of rejection. Positivity criteria for DSA was MFI >500 for test 1, while specificity assignation respected provider's recommendations for test 2. Results In G1, we identified at least 1 DSA in 44 patients with test 1, and in 39 patients with test 2. In G2, test 1 identified at least 1 DSA in 16 patients (32%) and test 2 in 7 patients (14 %). Sensitivity and specificity for ABMR diagnosis was 88% and 68% respectively with One Lambda, and 78% and 86% respectively with Immucor. Correlation and agreement were found in class I and II between intensity parameters of the 2 manufacturers. The use of the sum of the intensity of DSA (sDSA) improved the sensitivity and specificity of the 2 tests. Conclusions We report the first comparative study of the 2 Luminex assays available for detecting DSA in the post kidney transplant setting. Although there is a good correlation and reliability between the 2 assays, significant differences exist. Positivity criteria for DSA determination differ and interpretation should take these specificities into account. * Corresponding author: Dominique Bertrand, MD, Rouen University Hospital, 1 rue de Germont 76000 Rouen, France, dominique.bertrand@chu-rouen.fr Authorship: DB: performed research, collected data, analyzed data, and wrote the paper. FF, FHam, FHau: collected the data, performed research. DG: contributed to the revision and approval of the paper. All the others authors: collected data and contributed to the approval of the paper. Funding The authors have declared no funding. Disclosure: All of the authors of this manuscript have no conflicts of interest to disclose as described by Transplantation. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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