THROMBIN-ANTITHROMBIN III COMPLEX - A NEW PARAMETER FOR DETECTION OF THROMBOTIC STATES

Recently, we have developed an enzyme-linked immunosorbent assay (ELISA) for determination of thrombin-antithrombin III complex (TAT) in numan plasma (1). The test system follows the sandwich principle and uses two different antibodies directed against human thrombin and human antithrombin III, respectively. The antibodies bind selectively to the corresponding antigen moieties of TAT. The assay was calibrated with definite concentrations (2.0 to 60 μg/l) of preformed purified TAT added to TAT-poor plasma. Plots of absorbance 492 nm against TAT concentration revealed a linear correlation (r = 0.98). The lower limit of sensitivity of the assay was 0.5 μg/l. Mean coefficients of variation of 4 % (intraassay) and 7.5 % (interassay) were found for TAT concentrations between 2 and 60 μg/l. A reference range from 0.85 to 3.0 μg/l was calculated from TAT concentration in plasma samples from 88 healthy donors (mean value ± SD: 1.45 ± 0.4 μg/l). In plasma samples from patients with pulmonary embolism confirmed by lung-scan (n = 17), TAT concentrations between 10 and 20 μg/l were measured. In patients with deep vein thrombosis confirmed by phlebography (n = 15), TAT were found up to 7 - 13 μg/l. Patients with septicaemia associated with a consumption coagulopathy (n = 10), and patients with acute hepatic failure (n = 5) showed markedly increased TAT values. In plasma samples from patients with various metastatic malignant diseases, TAT concentrations of 30 to 60 μg/l could be measured. From these data we conclude that measurement of TAT can be a sensitive parameter for specific detection of a latent activation of the clotting pathway.