The Biorex Diagnostics PT reagent is an in vitro diagnostic assay intended for use in performing the one stage prothrombin time (PT) test and assays which are based on a modified prothrombin time.

The prothrombin time is the method of choice for monitoring oral anticoagulation therapy and is a fundamental screening test for acquired or inherited bleeding disorders. During oral anti-coagulation therapy, the activity of vitamin K-dependent clotting factors (II, VII, IX, X, Protein C and Protein S) is reduced and PT time is increased. The test is used for quantitative determination of blood clotting factors in the extrinsic (VII) and common pathways (II, V and X) of coagulation.