[Evaluation of a new enzyme immunoassay method for determination of t-PA-PAI-1 complex]

We evaluated a new enzyme immunoassay for determination of t-PA-PAI-1 complex (PAI-C) and studied the clinical utility of measuring PAI-C. This assay was performed by the capture/tag antibody technique using polystylene beads, in which the beads were coated with monoclonal antibody against PAI-1 and anti-t-PA polyclonal antibody was tagged (TDC-88, TEIJIN-LIMITED, Japan). The assay gave an excellent sensitivity with a detection limit of 0.1 ng/ml, and we were able to detect a trace amount of PAI-C in normal plasma. PAI-C in 6 volunteers showed significant daytime fluctuations. The normal value of PAI-C in plasma was below 13.8 ng/ml (n = 40). PAI-C levels in patients with accelerated fibrinolysis (n = 31) ranged from 2.9 to 66.4 ng/ml and 15 of them were outside the normal range. However, all of patients with DIC (n = 10) showed abnormally high PAI-C levels. In patients with accelerated fibrinolysis, PAI-C values correlated with t-PA antigen (r = 0.838), PAI-1 antigen (r = 0.519), ATIII activity (r = -0.669) (p less than 0.01) and D dimer levels (r = 0.391, p less than 0.05). However, PAI-C values did not correlate with plasminogen and alpha 2PI activity, alpha 2PI-plasmin complex or the FDP-E level in these patients. Our data suggests that PAI-C may be a new molecular marker that reflects t-PA release from endothelial cells and a useful indicator to study hypercoagulable states.