Thrombin-activatable fibrinolysis inhibitor antigen levels and cardiovascular risk factors.

Thrombin-activatable fibrinolysis inhibitor (TAFI) is a recently described fibrinolysis inhibitor that circulates in plasma as a procarboxypeptidase and is converted into an active form during coagulation. The physiological relevance of TAFI is not known, but it might be involved in pathways regulating fibrin deposition. Our aim was to determine the interindividual variability of plasma TAFI antigen values and their associations with conventional cardiovascular risk factors. Six hundred twenty-six consecutive patients (277 men) attending a metabolic ward for primary prevention were studied. TAFI antigen presented a large range of values, with a 2- to 3-fold increase between the 10th and 90th percentiles. No difference was observed between the 2 sexes. A significant correlation was observed between age and TAFI levels in women only. After adjustment for age, TAFI antigen was positively correlated in men for the waist-to-hip circumference ratio and blood pressure, whereas no significant correlation was observed in women. Stepwise multiple linear regression analysis indicated a low contribution of the parameters studied to the variability of TAFI antigen levels; the waist-to-hip circumference ratio accounted for only 2% in men, and age accounted for only 3% in women. Results were compared with those of fibrinogen and plasminogen activator inhibitor-1; cardiovascular risk factors in men and women accounted for 16% and 9. 5%, respectively, of the fibrinogen variance and 36% and 32%, respectively, of the plasminogen activator inhibitor-1 variance. These observations did not attribute an important role to lifestyle characteristics in the control of TAFI antigen concentration in plasma. Because of the large interindividual variability of TAFI levels in plasma, genetic control may be involved.