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 mean fluorescence intensity greater than 500 for test 1, whereas specificity assignation respected the 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 (32%) patients and test 2 in 7 (14%) patients. Sensitivity and specificity for antibody-mediated rejection 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 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 postkidney 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.