Which test is used to monitor anticoagulation therapy intensity in patients taking warfarin?

Which test is used to monitor anticoagulation therapy intensity in patients taking warfarin?

• A. WBC
• B. Platelet
• C. PT
• D. INR

Answer: (D)

Monitoring the effect of warfarin relies on the International Normalized Ratio (INR), which is the standardized form of the prothrombin time (PT). Warfarin slows the production of vitamin K–dependent clotting factors, so the PT measures how long blood takes to clot. However, PT results vary with different lab reagents and methods. The INR adjusts for these differences, providing a consistent value to guide dosing across laboratories. Clinicians aim for a target INR range (often around 2.0–3.0, depending on the condition). WBC and platelet counts are not used to measure warfarin intensity, so they don’t serve this monitoring purpose.

Monitoring the effect of warfarin relies on the International Normalized Ratio (INR), which is the standardized form of the prothrombin time (PT). Warfarin slows the production of vitamin K–dependent clotting factors, so the PT measures how long blood takes to clot. However, PT results vary with different lab reagents and methods. The INR adjusts for these differences, providing a consistent value to guide dosing across laboratories. Clinicians aim for a target INR range (often around 2.0–3.0, depending on the condition). WBC and platelet counts are not used to measure warfarin intensity, so they don’t serve this monitoring purpose.