This article is more than 5 years old. Information may no longer be current.
INR stability inconsistent among patients with AF assigned warfarin
Click Here to Manage Email Alerts
Patients with atrial fibrillation assigned warfarin for stroke prevention who have a stable INR often do not maintain that stability, according to a research letter published in JAMA.
Sean D. Pokorney, MD, from the division of cardiology, Duke University Medical Center, and colleagues analyzed data from 3,749 patients (mean age, 75 years; 43% women) from the ORBIT-AF registry between June 2010 and August 2011. Follow-up occurred up to 3 years through November 2014.
Sean D. Pokorney
The researchers analyzed whether patients with AF assigned warfarin who have stable INR values remain that way long term.
“Whether patients previously stable on warfarin should be switched to non-vitamin K oral anticoagulants remains controversial but may be informed by determining whether patients receiving warfarin who have stable INR values remain stable over time,” Pokorney and colleagues wrote.
According to the study background, non-vitamin K oral anticoagulants are safer and more effective compared with warfarin, but also more costly.
Of the cohort, 968 patients (26%) had stable INR, defined as 80% or more of INR values in the 2 to 3 range at 6 months, and 34% of those (95% CI, 31-37) remained stable the following year.
Of the 376 patients (10%) with 100% of INR values in range at 6 months, 37% (95% CI, 32-42) showed stability during the following year, the researchers wrote.
Among patients with 80% or more INR values in range at baseline, 36% (95% CI, 33-39) had one or more well-out-of-range INR values in the next year. There is limited predictive ability regarding stability on well-out-of-range INR values (C index = 0.57; 95% CI, 0.56-0.59), according to the researchers.
Of the 32% of patients (95% CI, 31-34) with a time in therapeutic range of at least 80% at 6 months, 38% (95% CI, 35-41) had at least one INR well out of range during the following year, Pokorney and colleagues wrote.
“A common belief has been that patients with stable [INR values] while taking warfarin would continue to be stable and derive less benefit from switching to non-vitamin K oral anticoagulants,” the researchers wrote. “This analysis suggests warfarin stability is difficult to predict and challenges the notion that patients who have done well taking warfarin should maintain taking warfarin.” – by James Clark
Disclosure: Pokorney reports receiving grants from AstraZeneca, Boston Scientific and Gilead, receiving consultant fees from Boston Scientific and Medtronic, and serving on an advisory board for Janssen. Please see the full study for a list of the other researchers’ relevant financial disclosures.
Click Here to Manage Email Alerts