An early evaluation of the HISTO SPOT® AB ID Class I & II test in cardiothoracic transplant patients

The HISTO SPOT^®AB ID assay (BAG Diagnostics GmbH) is a novel single antigen HLA Class I & II antibody definition test used with the MR.SPOT^® processor. We compared this assay with Luminex^®-based assays to assess its potential application in defining unacceptable antigens for transplantation in patients awaiting transplants with cardiothoracic organs. A cohort of 40 sensitized cardiothoracic patients were identified, and one sample was selected from each patient. The required screening was based on the patients’ antibody profiles (Class I, n = 17, Class II, n = 11, Class I & II, n = 12). Samples were screened with LABScreen™ Single Antigen (SAg), LIFECODES^® LSA™, HISTO SPOT^® AB ID, and an acid modified LABScreen™ SAg test for detecting antibodies against denatured HLA. Results indicated that HISTO SPOT^® AB ID had reduced sensitivity (68% for Class I; 69% for Class II). When compared to LABScreen™ and LIFECODES^®, HISTO SPOT^® AB ID failed to detect Luminex^®-defined antibodies with median fluorescence intensity (MFI) ranging from 1114 to 24,489. The HISTO SPOT^® AB ID panel used in the study had reduced antigen representation compared with Luminex^®-based assays which further compromised its capacity for antibody detection and definition. Further work is needed to evaluate the clinical relevance of these differences between the performance of HISTO SPOT^® and Luminex^®-based methods.