Positive single-antigen bead assay with negative flow crossmatch in a renal transplant-A case report

The occasion is when there is discordance between the results of the cell-based and virtual crossmatch and requires further workup before considering a patient for renal transplant. A case of the positive single-antigen bead (SAB) with donor-specific antibodies (DSA) against HLA-A*33:01 with negative complement-dependent cytotoxicity crossmatch and flow crossmatch was identified. The acid treatments of the beads were done to denature the antigen to understand the nature of identified DSA. There was variation in the Mean fluorescence intensity (MFI) observed in between patient sera with acid-treated beads (significantly increased) in contrast to regularly untreated SAB. This indicated additional antigens become available by the denaturation process. Hence, before making a final decision about the transplant in cases of ambiguity, SAB results should be interpreted in light of other compatibility results.