Which tests are used to monitor Coumadin/Warfarin therapy?

Which tests are used to monitor Coumadin/Warfarin therapy?

• A. PT and INR
• B. PTT and ACT
• C. PT only
• D. INR only

Answer: (A)

Warfarin works by slowing the extrinsic pathway, so monitoring relies on the prothrombin time, which measures how long plasma takes to clot after tissue factor is added. Because PT results vary with different reagents, the international normalized ratio (INR) is used to standardize the result across laboratories. Together, PT and INR provide a reliable measure to adjust warfarin dosing and maintain the desired level of anticoagulation. Tests like PTT or ACT assess the intrinsic pathway and are used for heparin therapy, not routine warfarin monitoring. Thus, the combination of PT and INR is the best choice for monitoring Coumadin/Warfarin therapy.

Warfarin works by slowing the extrinsic pathway, so monitoring relies on the prothrombin time, which measures how long plasma takes to clot after tissue factor is added. Because PT results vary with different reagents, the international normalized ratio (INR) is used to standardize the result across laboratories. Together, PT and INR provide a reliable measure to adjust warfarin dosing and maintain the desired level of anticoagulation. Tests like PTT or ACT assess the intrinsic pathway and are used for heparin therapy, not routine warfarin monitoring. Thus, the combination of PT and INR is the best choice for monitoring Coumadin/Warfarin therapy.