What test is commonly used to monitor warfarin therapy?

The International Normalized Ratio (INR) is the standard test used to monitor patients on warfarin therapy. Warfarin is an anticoagulant that works by inhibiting vitamin K-dependent clotting factors, which are essential for blood coagulation. The INR provides a standardized way to measure the effectiveness and safety of warfarin therapy across different laboratories, ensuring that results are consistent regardless of where the test is performed.

The INR is calculated based on the prothrombin time (PT) results, adjusted for the specific testing methods used in different laboratories, allowing healthcare providers to maintain the therapeutic range for patients on warfarin. This is critical since the therapeutic window for warfarin is narrow, requiring careful monitoring to avoid complications such as thrombosis or bleeding. Therefore, the use of INR is essential for dosing adjustments and overall management of patients receiving warfarin treatment.

Other tests, such as Activated Partial Thromboplastin Time (APTT) and Thrombin Time (TT), measure different aspects of the coagulation pathway and are not routinely used for monitoring warfarin. Ecarin time is used in specific contexts, mainly related to testing direct thrombin inhibitors, and also does not apply to warfarin