Chromogenix Coamatic® LR Antithrombin is an assay kit for the quantitative determination of the heparin cofactor activity of antithrombin (AT) in human citrated plasma. All components of the antithrombin test kit are in liquid formulation (LR=Liquid Reagents).

Reagents, Packaging, Storage and Stability

  1. Substrate solution S-2772™, 26 mg, 2 vials Contains chromogenic substrate S-2772™ (Ac-D-Arg-Gly-Arg-pNA·2HCl) in tartaric acid buffer pH 4.2. Stability once opened: 6 months at 2-8°C in the original vial.
  2. Factor Xa solution, 90 nkat, 6 vials Contains purified bovine Factor Xa, bovine albumin and heparin, in Tris buffer, pH 8.2. Stability once opened: 1 month at 2-8°C in the original vial.

Unopened reagents and calibrator are stable until the expiration date shown on the vial when stored at 2-8°C. WARNING: Do not use reagents beyond the expiry date printed on the package label. Discard if the substrate solution appears yellow. Avoid contamination by microorganisms.

AT + Heparin ————–> [AT · Heparin]
[AT · Heparin] + FXa (excess) ————–> [AT · Heparin · FXa] + FXa (residual)
FXa (residual)
S-2772™ ————–> Peptide + pNA

AT = Antithrombin

Antithrombin is the most important natural inhibitor of the coagulation cascade. By inhibiting the coagulation proteases, especially thrombin, factor Xa and factor IXa, antithrombin prevents uncontrolled coagulation and thrombosis. Plasma is incubated with an excess of Factor Xa (FXa) in the presence of heparin. The residual activity of FXa is determined by the rate of hydrolysis of the chromogenic substrate S-2772™. The pNA release measured at 405 nm is inversely proportional to the AT level in the range 15 -125% of normal plasma. Read more…