An enzyme-linked immunosorbent assay (ELISA) was developed for the determination of
thrombin-antithrombin III complex (TAT) in human plasma. 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 of
preformed purified TAT added to TAT-poor plasma. The lower limit of sensitivity of
the assay was 0.5 μg/1. Mean coefficients of variation of 4.2% (intraassay) and 3.5%
(interassay) were found for TAT concentrations between 2 and 60 μg/1. A reference
range from 0.85 to 3.2 μg/1 was calculated from TAT concentration in plasma samples
from 88 healthy donors (mean value ± SD: 1.45 ± 0.4 μg/I). In plasma samples from
patients with pulmonary embolism (n = 17), TAT concentrations between 3 and 25 μg/1
were measured. In 15 patients with deep vein thrombosis, TAT was found up to 3 to
25 μg/1. 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.
Key words
Thrombin - antithrombin III complex - ELISA
