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Physiology & Biochemistry · single question

All of the following statements about INR (International Normalized Ratio) are TRUE EXCEPT:

  1. It is used to monitor warfarin (vitamin K antagonist) therapy
  2. The therapeutic range is generally about 2-3 for most indications
  3. A result must be periodically rechecked — it does not remain valid for many months
  4. It directly measures glycated hemoglobin (HbA1c), reflecting average blood glucose control over about 3 months
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Correct answer: D. It directly measures glycated hemoglobin (HbA1c), reflecting average blood glucose control over about 3 months

This is the false statement — INR reflects clotting tendency (specifically the extrinsic/common coagulation pathway, standardized for monitoring warfarin), while HbA1c is a completely separate test reflecting long-term blood glucose control. Don't confuse the two. INR also needs frequent rechecking (often every few weeks for stable patients on warfarin), not every 6 months.

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