A ONE-STEP ENZYME-IMMUNOASSAY FOR TOTAL PLASMINOGEN-ACTIVATOR INHIBITOR-1 ANTIGEN IN HUMAN PLASMA

A one-step enzyme immunoassay (EIA) has been developed for plasminogen activator inhibitor-1 (PAI-1) antigen. The assay is based on polyclonal antibodies, which were found to be slightly more reactive with tissue-type plasminogen activator (t-PA)/PAI-1 complexes and latent PAI-1 than with active PAI-1. To correct this, active PAI-1 is converted to t-PA/PAI-1 complexes. Latent PAI-1 and t-PA/PAI-1 complexes were equally reactive. The EIA is specific (PAI-2 and PAI-3 are not detected), precise (CVs range from 1.8% to 11.1%, depending on the PAI-1 concentration), fast (assay time less than 3 h), and easy to perform. It is compatible with the use of Stabilyte(R) plasma. The assay is calibrated against the putative international standard of the National Institute of Biological Standards and Control (NIBSC; lot 87/512). The normal ranges found with this EIA were 13.2-88 ng/ml; one apparently normal donor had a value of 100 ng/ml.