Characterization of HLA class I specific antibodies by ELISA using solubilized antigen targets: I. Evaluation of the GTI QuikID assay and analysis ofantibody patterns

The development of solid phase immunoassays using solubilized HLA molecules as targets has provided a means of detecting HLA-specific antibodies that overcomes many of the shortcomings of lymphocyte based assays. We have eval uated a commercially available assay, the GTI QuikID (QID), that uses solub ilized class I molecules from 40 subjects select-ed for their HLA phenotype , to characterize HLA-specific antibodies. We tested 595 sera from 319 subj ects and compared the results obtained with QID to those obtained with cyto toxicity (CYT) and with GTI QuikScreen (QS) as well as to historic data. Th e correlation of QID with CYT (r = 0.54) vas comparable to that between QID and QS (r = 0.60) : The-majority of disparities between QS and QID were ap parent false negatives with QID that could be overcome by analyzing QID dat a at lower cutoff values. In contrast, mosi: of the disparities between QID and CYT were false negatives in CYT due to the relatively low sensitivity of that assay. As expected, the ELISA was more sensitive (97%) than CYT (78 %) but bad a somewhat lower specificity (87% vs. 92%) due, most likely, to selection of sera that excluded most sera that were known to be nonspecific by CYT. Determination of antibody specificity could be achieved quickly by manual analysis of the QID data because of the way the data are presented by the manufacturer's software. Interestingly, the frequencies of different antibodies detected by ELISA differed from those detected by CYT with ELIS A identifying more sera containing antibodies to both A and B locus antigen s. (C) American Society for Histocompatibility and Immunogenetics, 2001.. P ublished by Elsevier Science Inc.