Henry Bussey, PharmD
Potential Conflicts of Interest:Consultancies: Genesis Advanced Technologies. Stock ownership or options (other than mutual funds): Inverness Medical. Patents received/pending: 3 vitamin K antagonist products.
Bussey H. The Net Clinical Benefit of Warfarin Anticoagulation in Atrial Fibrillation. Ann Intern Med. 2010;152:264-265. doi: 10.7326/0003-4819-152-4-201002160-00016
Download citation file:
Published: Ann Intern Med. 2010;152(4):264-265.
TO THE EDITOR:
With regard to the article by Singer and colleagues (1), calculating net clinical benefit of warfarin therapy in atrial fibrillation is an important concept (2). However, 3 other issues should be considered in the future.
First, warfarin therapy affects other major events and may substantially reduce myocardial infarction and death (3).
Second, because control of the international normalized ratio (INR) varies in different settings and because a 10% improvement in the amount of time the INR is in the therapeutic range (TTR) has been associated with a greater than 10% reduction in event rates (3, 4), the relationship between INR control and event rates must be more thoroughly defined before it can be determined how INR control may affect the net clinical benefit in one's own setting. Veeger and colleagues (5) found that the bottom quartile of approximately 4000 patients was in range only 10% to 20% of the time and accounted for more than half of the major events. Jones and colleagues (4) found that the bottom quartile of 2223 patients was in range only about 28% of the time. Furthermore, because event rates increase exponentially as the INR moves further out of range, being slightly out of the target range may have little effect, whereas being at the extremes (INR, <1.5 or >5.0) may carry a very high risk. Therefore, one must know what the event rates were when the INR was in the target range TTR ± 0.3 INR units, below an INR of 1.5, and above an INR of 5.0 to estimate the net clinical benefit in one's own setting.
to gain full access to the content and tools.
Learn more about subscription options.
Register Now for a free account.
Copyright © 2016 American College of Physicians. All Rights Reserved.
Print ISSN: 0003-4819 | Online ISSN: 1539-3704
Conditions of Use
This PDF is available to Subscribers Only