A patient taking Warfarin requires dental treatment. Which laboratory test should be obtained to assess anticoagulation status?

The International Normalized Ratio (INR) is the standardized measure used to monitor anticoagulation therapy with warfarin (Coumadin). Warfarin inhibits vitamin K-dependent clotting factors (II, VII, IX, X). The therapeutic INR range for most indications is 2.0 to 3.0. For routine dental procedures, an INR up to 3.5 is generally considered safe with local hemostatic measures. An INR greater than 3.5 to 4.0 warrants physician consultation before invasive dental procedures. The INR is standardized to allow consistent interpretation across different laboratories, unlike the prothrombin time (PT) alone.