Plasminogen activator inhibitor (PAI) activity was measured by a newly developed assay (PAI-test, Behringwerke AG) in 17 healthy subjects, 52 patients with thrombotic disease, seven patients with sepsis and three pregnent women. This assay method uses an oxidant which destroys α2-plasmin inhibitor activity, and acidification and dilution steps of plasma samples could be eliminated. The mean PAI activity was 0.67±SD0.60 u-PA inhibiting units/ml (U/ml) in healthy subjects; men had somewhat higher mean PAI levels than women (0.81 vs 0.54U/ml). Some patients with thrombotic diseases had elevated PAT values (1.04±1.09U/ml), and their PAI values correlated with tissuetype plasminogen activator (t-PA) antigen but not with plasmin-α2-plasmin inhibitor complex. Increased PAI levels were found in patients with sepsis (3.66±3.22U/ml) and in pregnant women (7.80±4.45U/ml), Further studies of larger series of patients would provide more precise information about the clinical implication of high PAI states.
