Determination of Anti-HLA Antibody Positivity in Kidney Transplant Candidates in a Tissue Typing Laboratory and Results Analysis.

Background: To retrospectively investigate the correlation between anti-HLA antibody PRA identification and single antigen bead (SAB) results and the relationship between mean fluorescence intensity (MFI) values determined using Luminex-based techniques and complement-dependent cytotoxicity (CDC-XM) and flow cytometry (FC-XM) results.

Material and method: Between 2017 and 2020, 256 patients with end-stage renal disease who were admitted to the Tissue Typing Laboratory of Istanbul Faculty of Medicine and tested for anti-HLA antibodies were included in the study. The correlation between antigen-specific antibody identification, SAB, CDC-XM, and FC-XM tests was analyzed retrospectively.

Results: PRA identification was positive in 78.5% of the patients. Of these patients, 15.2% were class I positive and 31.6% were class II positive. In the SAB test, 171 patients (66.8%) were positive. Of the SAB-positive patients, 16.8% were SAB-I positive and 24.2% were SAB-II positive. Fifty-two percent of patients were FC-XM positive and 10.5% were CDC-XM positive. SAB-I MFI>5141 and SAB-II MFI>7649 values were significantly correlated with positive CDC-XM (p < .001 and p = .048, respectively). SAB-I MFI>2721 and SAB-II MFI>2719 values were correlated with positive FC-XM-B (p = .003 and p = .038, respectively). The highest MFI values for identification were HLA-A:20896, HLA-B:18100, HLA-DRB1:21054, HLA-DQ:24034, and HLA-A:15715, HLA-B:11002, HLA-DR:22400, HLA-DQB1:22700, and DQA1:14782 for SAB.

Conclusion: In our study, it was found that some low-titer antibodies that could not be identified using PRA could be detected using SAB. We think it is important to evaluate SAB tests in these patients and to include this region in HLA typing reports because antibodies frequently develop in the HLA-DQA1 region.