Medical Emergencies · single question
A patient on warfarin requires a dental extraction. Which laboratory test is ESSENTIAL to perform?
Show answer and explanation
Correct answer: A. PT/INR
A) PT/INR — CORRECT.
Warfarin inhibits Vitamin K-dependent clotting factors (II, VII, IX, X). The International Normalized Ratio (INR), derived from the Prothrombin Time (PT), specifically monitors warfarin therapy. Before extraction, INR should be ≤ 3.5 (ideally 2.0–3.5) for routine procedures. The target therapeutic INR is 2.0–3.0 for most indications.
B) PTT/aPTT: Monitors heparin therapy and the intrinsic pathway — not warfarin.
C) CBC/platelet count: Important but not specific to warfarin monitoring.
D) Bleeding time: Assesses platelet function — not affected by warfarin (a coagulation factor inhibitor).
Warfarin inhibits Vitamin K-dependent clotting factors (II, VII, IX, X). The International Normalized Ratio (INR), derived from the Prothrombin Time (PT), specifically monitors warfarin therapy. Before extraction, INR should be ≤ 3.5 (ideally 2.0–3.5) for routine procedures. The target therapeutic INR is 2.0–3.0 for most indications.
B) PTT/aPTT: Monitors heparin therapy and the intrinsic pathway — not warfarin.
C) CBC/platelet count: Important but not specific to warfarin monitoring.
D) Bleeding time: Assesses platelet function — not affected by warfarin (a coagulation factor inhibitor).
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