(h)PT-Phen (4)

Intended Use

(h)PT-Phen (4) reagent is a thromboplastin reagent (containing recombinant human tissue factor, synthetic phospholipids and calcium at an optimized concentration) for the determination of prothrombin time (PT), in human citrated plasma, using a clotting method, manual or automated.

Summary and Explanation

The prothrombin time (PT) is a one-stage test based on the Quick method. The PT assesses the overall activity of clotting factors of the extrinsic pathway (coagulation triggered by contact with thromboplastin expressed by specific cells). This test is used to explore abnormalities of factors II, V, VII, X and fibrinogen in congenital or acquired bleeding disorders), liver disease, vitamin K deficiency, disorders of fibrinolysis and disseminated intravascular coagulation. PT test is the most commonly used coagulation assay for laboratory monitoring of anticoagulant therapy by vitamin K antagonists (VKA). Any isolated prolongation of PT, not associated with Vitamin K Antagonist (VKA) therapy has to be explored by individual assay of factors involved in the extrinsic coagulation pathway (FII, VII, V, X).

PT does not explore factor deficiencies of the intrinsic coagulation pathway (Factors VIII, IX, XI, and XII), platelets, Factor XIII or natural inhibitors of coagulation (Antithrombin, Protein C and Protein S).

Assay Principle

Prothrombin time is the determination of a clotting time at 37°C in the presence of thromboplastin and calcium. Complex tissue factor-FVIIa activated factor X, then generation of thrombin, leading to fibrin formation. The clotting time is depending on the activity of extrinsic pathway coagulation factors. The measured PT can be converted to concentration or expressed as “International Normalized Ratio (INR)”.