An early evaluation of the HISTOSPOT (R) ABIDClass I & II test in cardiothoracic transplant patients

The HISTO SPOT (R) AB ID assay (BAG Diagnostics GmbH) is a novel single antigen HLA Class I & II antibody definition test used with the MR.SPOT (R) processor. We compared this assay with Luminex (R)-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 LABScreenT Single Antigen (SAg), LIFECODES (R) LSAT, HISTOSPOT (R) ABID, and an acid modified LABScreenT SAg test for detecting antibodies against denatured HLA. Results indicated that HISTO SPOT (R) AB ID had reduced sensitivity (68% for Class I; 69% for Class II). When compared to LABScreenT and LIFECODES (R), HISTOSPOT (R) AB ID failed to detect Luminex (R)-defined antibodies with median fluorescence intensity (MFI) ranging from 1114 to 24,489. The HISTO SPOT (R) AB ID panel used in the study had reduced antigen representation compared with Luminex (R)-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 HISTOSPOT (R) and Luminex (R)-based methods.