Prothrombin Time (PT)
PT with Calcium
The capacity of blood to form a fibrin clot by means of the extrinsic hemostatic pathway requires thromboplastin, calcium, factors I, II, V, VII and X. The PT-HS reagent provides a source of tissue thromboplastin and calcium that specifically activates factor VII in the extrinsic coagulation pathway.
The factors involved in the intrinsic coagulation pathway are bypassed. Therefore, deficiencies of intrinsic pathway factors (VIII, IX and XII) are not detected using the PT test.