Antibody monitoring system to support the single-antigen Luminex assay in donor-specific antibody detection

The antibody monitoring system (AMS) is a crossmatch test using enzyme-linked immunoassay to detect donor-specific anti-HLA antibodies (DSA). The aim of this study was to determine whether the AMS assay is useful for supporting DSA results measured with single-antigen Luminex assay (Luminex-DSA) in renal transplant recipients. Thirty sera from 12 sensitized recipients and 71 sera from 60 nonsensitized recipients were screened by complement-dependent cytotoxic crossmatch (CDC-XM), flow cytometric crossmatch (FCXM), AMS, and the Luminex assays. Twenty-two sera (73.3%) from sensitized patients were positive for Luminex-DSA, and the AMS assay revealed the great specificity and positive predictive value for detecting Luminex-DSA in sera from sensitized patients. Positivity in the AMS assay was observed most frequently in Luminex-DSA–positive sera with ≥10,000 mean fluorescence intensity (MFI) levels (66.7%). Of the 101 sera, the results of the AMS assay were compatible with CDC-XM results in 73 sera (91.3%) and with FCXM results in 72 sera (90.0%); these rates were significantly higher for the AMS assay than for the Luminex assay (p = 0.008 for CDC-XM and p = 0.001 for FCXM). In conclusion, the AMS assay is useful as a supportive solid-phase method for predicting actual crossmatch and high level of Luminex-DSA in sensitized patients.