PT (INR) test kit is used for the determination of prothrombin complex-activity in whole blood according to Owren. It is ideal for monitoring of oral anticoagulation with vitamin-K inhibitors like Warfarin or Marcumar.
PT, according to Owren, measures the combined activity of the vitamin-K dependent coagulation factors II, VII and X. In analysis, the sample is mixed with thromboplastin, CaCl, fibrinogen and coagulation factor V.
The clotting time is prolonged on the therapeutical level (<0.4 IU/mL) of factor II, V and X in the sample, but the assay is insensitive to heparin in therapeutical levels up to 1.0 IE/mL.