The correlation of results of panel reactive antibody, identification, and single antigen beads in detection of anti-HLA antibodies: Istanbul Faculty of Medicine, tissue typing laboratory experience.

BACKGROUND:We have performed a retrospective analysis of anti-HLA class I MHC and class II MHC antibodies measured using a single antigen bead (SAB) assay and a panel reactive antibody (PRA) assay. MATERIAL AND METHODS:A group of 256 patients with end-stage renal disease (ESRD) was tested for anti-HLA antibodies in the tissue typing laboratory between 2017 and 2020. In the cohort, the serum samples of patients waiting for transplantation were tested. Both the PRA and SAB tests of these patients were analyzed using the Luminex (Immucor) method. The threshold of positivity was accepted as median fluorescence intensities (MFI) ≥1000 for PRA screening and MFI ≥750 for SAB screening. RESULTS:Overall, antibodies to HLA antigens were detected in 202 (78.9%) out of 256 patients in the PRA study. Antibodies against both class I/II antigens were detected only in 15.6% of these patients, whereas antibodies against only against class I HLA in 31.3% and only against class II HLA in 32.0%. By comparison, the SAB study found that 66.8% of patients were positive for HLA antigens. Furthermore, donor-specific antibodies (DSA) were detected in 52.0% of PRA-positive patients and 52.6% of SAB-positive patients. It was shown that 168 patients (83.2%) out of 202 PRA-positive patients were found to be SAB-positive. In addition, 51 patients negative in the SAB assay (94.4%) were also negative in the PRA assay. Statistical analysis established a significant correlation between the PRA and SAB positivity (p > 0.001). It was also shown that MFI ≥3000 PRA positivity for class I HLA antigens (p = 0.049) and MFI ≥5000 PRA positivity for class II antigens (p < 0.001) correlated with the SAB positivity in patients. CONCLUSION:Our results showed the importance of both PRA and SAB assays to define the status of sensitization in patients.