Antithrombin III, heparin cofactor and antifactor Xa in relation to age, sex and pathological condition.

Antithrombin III (At-III) activity and protein, heparin cofactor activity, antifactor Xa activity were determined in 200 healthy adults, evenly distributed within age and sex groups, in 60 patients with cerebral thrombosis and in 20 oral contraceptive users. There was a positive correlation between At-III protein and its activities in normal subjects and in patients with cerebral thrombosis. The mean At-III protein and heparin cofactor activity values decreased with age in men and in women of fertile age. The mean values of At-III protein and its activities did not show any variation in the patients with cerebral thrombosis when compared with the normals. In oral contraceptive users a positive correlation was also found between At-III protein and its activities, antifactor Xa activity excepted. The mean antifactor Xa activity value in these women decreased during treatment, whereas the other At-III activities and At-III protein were unchanged.