Detection of HLA class I-specific antibodies by the QuikScreen enzyme-linked immunosorbent assay.

The GTI QuikScreen test is an enzyme-linked immunosorbent assay (ELISA) that uses soluble HLA class I antigens as targets. In tests of 5,893 human serum specimens, we evaluated the reliability, sensitivity, and utility of the GTI QuikScreen test for detecting HLA class I-specific antibody. We found that the test could reliably detect HLA-specific antibodies of the immunoglobulin G (IgG) but not the IgM class. The degree of correlation with lymphocytotoxicity testing varied among the different serum sources, with the best correlation achieved with sera from renal transplant candidates (r > 0.7) and the poorest with sera from patients with end-stage liver disease (r 5 0.26), possibly because of elevated alkaline phosphatase levels in the liver patients. Test reproducibility was high (96%), and test failure rate was low (1.7%). The test sensitivity is comparable to that of the antiglobulin cytotoxicity and, possibly, even flow cytometric tests. There was a highly significant (P < 0.001) correlation between the optical densities obtained in the ELISA and the percent panel reactive antibody determined by cytotoxicity testing. Therefore, although designed only to determine the presence or absence of HLA-specific antibody, GTI QuikScreen test results also provided an indication of the extent of sensitization. The test is one of the most effective and efficient ways to determine if antibodies producing a positive result in crossmatch tests are specific for HLA class I antigens. As an adjunct to serum screening by cytotoxicity testing, the GTI QuikScreen test can produce a substantial savings of time and effort that reduces the cost to the laboratory and to the patient. One of the most important components of histocompatibility testing for transplantation and for platelet and leukocyte transfusion therapy is detection and characterization of antibodies reactive with the transplanted organ or tissue. Of the various alloantibodies that may be produced, those most commonly involved in organ rejection and tissue destruction are HLA specific (reviewed in reference 13). Failure to detect the presence of these antibodies in patients may result in graft loss, destruction of transfused platelets and leukocytes, unnecessary shipment of organs, and increased time and effort spent on crossmatches. On the other hand, the failure to recognize when antibodies are not HLA specific may prevent transplantation inappropriately. Historically, HLA-specific antibodies have been detected by the complement-dependent cytotoxicity (CDC) test, which requires viable lymphocytes from a panel of individuals selected to represent a wide array of HLA antigens. Characterization of the antibodies present in presensitized patients awaiting transplantation is invaluable for the reasons noted above. However, there are several problems inherent in the CDC assay. It utilizes viable lymphocytes, and factors that affect cell viability can compromise the accuracy of the test results. The effectiveness of rabbit serum, used as a source of complement and heterophile antibody, may vary greatly, and this variability in turn affects test sensitivity. The test cannot be applied to sera from patients being treated with cytotoxic antibodies, such as OKT3, without first removing or blocking those antibodies. The test does not differentiate HLA-specific from other cytotoxic antibodies. Finally, most renal transplant candidates have monthly