MEASUREMENT OF PROGRESSIVE ANTITHROMBIN (AT III) ACTIVITY USING ANTI IIa METHOD (#221122) INTENDED USE: Chromogenic assay for the quantitative determination of the “progressive” activity of Antithrombin (AT), heparin independent, in human citrated plasma using an anti IIa

ASSAY PRINCIPLE: Antithrombin is the major physiological coagulation inhibitor. It inhibits coagulation serine esterases, especially Thrombin, Factor Xa and Factor IXa, regulates coagulation pathway and prevents from thrombosis. In the absence of heparin, Antithrombin is a “slow acting”, progressive, inhibitor of coagulation serine esterases. The antithrombin Anti-IIa method is a method based on the inhibition of a constant amount of Thrombin (IIa), by the tested antithrombin (without addition of heparin, but with a prolonged inhibition time between Factor IIa and tested AT), and hydrolysis of a Thrombin specific chromogenic substrate, by Thrombin in excess. pNA is then released from the substrate. The amount of pNA released is then a relation of the residual Thrombin activity. There is an inverse relationship between the concentration of AT present in the tested plasma and color development, measured at 405 nm.