Assessment of Luminex Mean Fluorescence Intensity Values with Complement-Dependent Cytotoxicity Results in Detection of Antibodies Against Human Leucocyte Antigen

Introduction. Antibodies to human leukocyte antigens (HLA) are one of the major immune barriers to successful organ transplantation. In addition to complementdependent cytotoxicity (CDC) assay as a standard method for the HLA antibodies detection, more sensitive solid-phase assays like Luminex were introduced. The aim of this study was to define mean fluorescence intensity (MFI) cutoff values of HLA Class I antibodies detected by Luminex from those detected by CDC given the possibility to use only Luminex assay in HLA antibody screening. Methods. This is a retrospective analysis of the HLA antibody screening results of patients on a kidney transplant waiting list, performed at the Tissue Typing Laboratory, Clinical Hospital Center Rijeka, Croatia, from January 2012 to July 2019. The study included 1,665 sera tested in parallel by CDC and Luminex techniques. Results. Almost half sera contained HLA antibodies (47.9%), significantly more detected by the Luminex than a CDC method. Antibodies against HLA-A and HLA-B molecules had higher MFI values, relative to the HLA-C antibodies, as well as antibodies detected by Luminex and CDC than those detected by Luminex alone. A cutoff MFI≥9,204 for Luminex detected HLA Class I antibodies correlated with positivity in the CDC assay. Besides MFI, several factors need to be taken into consideration in interpreting test results to identify unacceptable antigen mismatch. Conclusion. The results of this analysis suggest that the current features of the Luminex technique provide the most benefit in the HLA antibody scre