How Often Must INR Be Checked in Patients Taking Warfarin in Stable Doses?

A randomized trial demonstrates no significant difference in time in therapeutic range between patients monitored every 4 weeks and those monitored every 12 weeks.

According to current guidelines, warfarin recipients should undergo international normalized ratio (INR) testing every 4 weeks. In a single-center trial in Canada, 250 patients receiving long-term warfarin therapy in doses that remained unchanged for at least 6 months were randomized to INR assessment every 12 weeks or every 4 weeks. Both groups underwent INR monitoring every 4 weeks; however, treating physicians in the 12-week assessment group only saw the patients' true values every 12 weeks (sham values within therapeutic range were reported during the intervals).

During 12 months of treatment, mean time in therapeutic range was 74% in the 4-week group and 72% in the 12-week group, a nonsignificant difference. Significantly fewer patients…

Reviewing Author

Joel M. Gore, MD

Disclosures

Grant/Research SupportNIH–National Heart, Lung, and Blood Institute

Joel M. Gore, MD

Disclosures

Grant/Research SupportNIH–National Heart, Lung, and Blood Institute

How Often Must INR Be Checked in Patients Taking Warfarin in Stable Doses?

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Reviewing Author