Clinical Chemistry, Vol 28, 2249-2253, Copyright © 1982 by American Association for Clinical Chemistry

Two automated methods for plasma antithrombin III compared, and the clinical significance of the results

W Prellwitz, KF Schmitt, M Machner, CJ Schuster and L Weilemann

Antithrombin III (AT III) activity was determined with two different new chromogenic substances--Chromozym-TH (Tos-Gly-Arg-p-nitroanilide; Boehringer Mannheim) and alpha-N-carbobenzyl-oxy-L-lysine-thiobenzyl ester (Du Pont)--with both a discrete (aca) and a centrifugal analyzer (COBAS BIO). The correlation between the Chromozym-TH/centrifugal analyzer and Du Pont ester/aca methods was good (r = 0.9890). Precision within and between runs was similar to that for typical enzymic determinations. AT III in plasma of 226 healthy men and women ranged from 76.6 to 141.1% (100% = "normal"). We found no significant differences ascribable to oral contraceptives. AT III activity was decreased in 27% of patients with acute thromboembolic diseases (n = 62), in 48% of patients the first day after abdominal operations without complications (n = 78), and in 100% of patients with reversible or irreversible shock (n = 58). In patients receiving continuous therapy with heparin (1500 USP units/h) we saw no decrease in AT III within 96 h of beginning treatment. Plasma from 14 of 16 patients with disseminated intravascular coagulopathy showed a decrease in AT III of from 17 to 51% of normal before and during heparin therapy. We then treated all 16 patients with AT III concentrate. During such treatment, AT III in plasma must be monitored over short intervals to assure that sufficiently high proportions of AT III (greater than 70% of normal) are reached.