[Plasminogen activator inhibitor 1--a new thrombosis risk marker]

The plasma activity of plasminogen activator inhibitor 1 (PAI-1) was measured in 278 clinically healthy subjects (98 men, 180 women; mean age 26 [18-50] years). In 198 of them there were factors increasing the risk of thrombosis, such as smoking, over-weight and/or oral contraceptives. PAI-1 activity was within normal range (less than 4 U/ml) in male nonsmokers of normal weight and in female nonsmokers not taking oral contraceptives. In male smokers (5.76 +/- 1.93 U/ml) and in overweight subjects of both sexes (7.49 +/- 1.87 U/ml) PAI-1 was increased up to 10.6 U/ml as an indication of decreased fibrinolysis capacity. Nonsmoking females on oral contraceptives had lower PAI-1 levels (2.72 +/- 0.86 U/ml) than nonsmokers without hormonal intake (3.21 +/- 1.03 U/ml; P less than 0.001). Apparently the increased risk of thrombosis that occurs on oral contraceptives is not due to increased PAI-1 activity.