Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 77-year-old woman is evaluated for frequently fluctuating INRs (<1.8 to >3.5) while taking warfarin therapy. She has undergone INR testing every 1 to 2 weeks and frequent warfarin dose adjustments. She reports a consistent dietary intake. Medical history is notable only for recurrent deep venous thrombosis. She takes no other medications.
On physical examination, vital signs are normal, as is the remainder of the examination.
Which of the following is the most appropriate next step in management?
A. Daily low-dose vitamin K supplementation
B. Genetic testing for cytochrome P-450 2C9 and vitamin K epoxide reductase complex-1 polymorphisms
C. Genetic testing for factor V Leiden
D. Warfarin cessation and aspirin initiation
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