Aim: Spurious single antigen beads (SAB) reactions can potentially interfere the assignment of HLA antibodies using Luminex-based platforms. The HISTO SPOT® HLA AB utilises an alternative technology to detect HLA antibodies in the form of a single antigen chip array. Here, we assessed the concordance between HISTO SPOT® HLA AB and One Lambda LABScreen in the assignment of anti-HLA antibodies.
Methods: Sera from the 2023 APHIA Quality Assurance Program (QAP, n=12) was tested using HISTO SPOT® HLA AB and HLA Class I (HLA-I) and HLA Class II (HLA-II) antibody assignments were compared with the reported consensus specificities. In addition, patient sera with questionable antibody profiles using LABScreen was tested using HISTO SPOT® HLA AB and results were compared with Halifaster Flow cross match (FXM) and Adsorption Crossmatch Cells and Elution (AXE) results (n=23). Sera was diluted, transferred into HISTO SPOT transwells containing immobilized HLA antigens and the assay run on the MR.SPOT® processor as per manufacturer’s instructions. Results were interpreted using the HISTO MATCH HLA AB software.
Results: A total of 361 HLA-I and 64 HLA-II specificities were detected using HISTO SPOT® HLA AB using sera from the APHIA QAP samples. 12/12 HLA-I and 11/12 HLA-II tests achieved a concordance of ≥80% with consensus, to satisfy the programs guidelines. In one sample, HISTO SPOT® failed to detect antibodies to HLA-DR14, -DR15, -DR51 and -DR53, which were all weakly detected by LABScreen. 15/23 serum with questionable antibody profiles by LABScreen tested with HISTO SPOT® HLA AB were concordant with FXM and/or AXE results. Of these 15 concordant results, 11 confirmed the LABScreen result as spurious (negative HISTO SPOT and negative FXM/AXE Results) and 8 were confirmed as accurate LABScreen results (positive HISTO SPOT® HLA AB and positive FXM/AXE results). However, 8/23 sera tested with HISTO SPOT® HLA AB were not concordant with FXM and/or AXE results.
Conclusion: The HISTO SPOT® HLA AB is a user-friendly platform that may be useful as an alternative or complementary technique to Luminex-based platforms. However, investigations of suspected false positive reactions require the utilisation of multiple technologies including different SAB kits, different platforms, and the addition of crossmatching techniques to be confident in the assignment of HLA antibodies.
