Risk of Ischemic Stroke Associated With Functional Thrombin-Activatable Fibrinolysis Inhibitor Plasma Levels

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Abstract
Background and Purpose— Recently, a novel procarboxypeptidase B–like proenzyme, called thrombin-activatable fibrinolysis inhibitor (TAFI), has been described. It plays an important role in the delicate balance between coagulation and fibrinolysis. TAFI leads to potent inhibition of tissue plasminogen activator–induced fibrinolysis. The relevance of TAFI in thromboembolic disease is unclear. We have investigated the risk of ischemic stroke (IS) in relation to plasma levels of functional TAFI. Methods— In a case-control study, we enrolled 264 individuals; 114 had IS, and 150 were recruited as controls who were age and sex matched and had no history of arterial disease. The individuals supplied information on their personal and family histories of cardiovascular diseases and conventional cardiovascular risk factors. Functional TAFI assays were performed by use of a method based on the activation of TAFI with thrombin-thrombomodulin and the measure of the TAFI activity generated. Other hemostatic parameters assayed were factor VIIIc, anti-phospholipid antibodies,fibrinogen, factor V Leiden, and the prothrombin gene G20210A mutations (PT20210A). Results— Functional TAFI levels were significantly higher in patients with IS (113.7±25%; range, 57% to 209%) than in controls (102.6±19%). The odds ratio for IS in patients with functional TAFI levels >120% was 5.7 (95% confidence interval, 2.3 to 14.1). Conclusions— We found that functional TAFI levels in plasma (>120%) increased the risk of IS ≈6-fold. Further studies should elucidate the physiological role of TAFI in arterial disease and possibly provide clues to therapeutic approaches.