[Antithrombin III: reference values found with a chromogenic substrate (chromozym TH) (author's transl)]

A new kinetic assay for antithrombin III (heparin-cofactor) in plasma was used to determine reference values. Ranges of 10--15 IU/ml at 25 degrees C and 20--29 IU/ml at 37 degrees C were found for a reference population of 219 men and 204 women 15--93 years of age. There was no evidence that these values vary with age or sex, nor was there any difference between pre- and postprandial antithrombin activities, or between smokers' and non-smokers' values. None of the illnesses present in the reference population nor any related drug therapy affected the antithrombin III level, and there was no statistically significant difference between the values for women taking oral contraceptives and those who did not. However, this latter observation does not preclude the possibility of individual variation.