Prothrombin Time (PT) is used to monitor which therapy?

Prothrombin Time (PT) is used to monitor which therapy?

• A. Heparin therapy
• B. Aspirin therapy
• C. Vitamin K therapy
• D. Warfarin therapy

Answer: (D)

Prothrombin Time is a measure of the extrinsic pathway of coagulation and is especially sensitive to the vitamin K–dependent clotting factors II, VII, IX, and X. Warfarin lowers the levels of these factors, causing a longer PT. Because of this direct relationship, PT (often reported as INR) is used to monitor and guide dosing of warfarin to keep anticoagulation within a target range. In contrast, heparin affects the intrinsic pathway and is monitored with the aPTT or anti-Xa assays. Aspirin mainly impairs platelet function, not the coagulation factors tested by PT, so PT isn’t used to monitor aspirin therapy. Vitamin K therapy affects coagulation factor production and can reverse warfarin’s effect, but it isn’t used to monitor anticoagulation with a target PT/INR in the way warfarin is.

Prothrombin Time is a measure of the extrinsic pathway of coagulation and is especially sensitive to the vitamin K–dependent clotting factors II, VII, IX, and X. Warfarin lowers the levels of these factors, causing a longer PT. Because of this direct relationship, PT (often reported as INR) is used to monitor and guide dosing of warfarin to keep anticoagulation within a target range.

In contrast, heparin affects the intrinsic pathway and is monitored with the aPTT or anti-Xa assays. Aspirin mainly impairs platelet function, not the coagulation factors tested by PT, so PT isn’t used to monitor aspirin therapy. Vitamin K therapy affects coagulation factor production and can reverse warfarin’s effect, but it isn’t used to monitor anticoagulation with a target PT/INR in the way warfarin is.