Adopting 2014 guidelines for reducing the risk of stroke in patients with atrial fibrillation would revise the number recommended for oral anticoagulation treatment in the U.S. upwards by 988,500, according to an analysis published online March 2 in JAMA Internal Medicine.

Emily C. O’Brien, PhD, of the Duke Clinical Research Institute in Durham, N.C., and colleagues explored the potential impact of changes in the American Heart Association, American College of Cardiology and Heart Rhythm’s most recent set of joint guidelines. The 2011 recommendations used the CHADS₂ score, which assesses the risk of stroke using factors such history of stroke, congestive heart failure, hypertension, diabetes and age beyond 75 years. The 2014 version bases risk on the CHA₂DS-VASc score, which adds female sex, vascular disease and age between 65 and 74 years to the mix. CHA₂DS-VASc also gives more weight to age over 75.

The researchers looked at data on 10,132 patients enrolled between May 2010 to October 2011 in the ORBIT-AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation) study. Based on that population, the proportion of patients who would be eligible for oral anticoagulation therapy would increase 19 percent under the broader 2014 recommendations.

Virtually all elderly and women patients would qualify for recommended treatment. The proportion of patients 65 and older would increase from 79.1 percent to 98.5 percent; for women, the change was 76.7 percent to 97.7 percent.

They identified 1,926 patients who would be reclassified under the new guidelines. Of those, 43.6 percent and 49.5 percent were deemed high risk because of one and two risk factors, respectively. Age was a factor in 81.4 percent of the reclassifications, being female in 46.8 percent and the presence of vascular disease in 35.1 percent.

Overall, two of three patients who previously would not have been recommended for therapy now were in the 2014 guidelines. Transferring those findings to the broader population in the U.S., they determined that 988,500 patients with atrial fibrillation would be reclassified under the 2014 guidelines as recommended for oral anticoagulation therapy.        

In an accompanying commentary, Margaret C. Fang, MD, MPH, of the University of California, San Francisco, pointed out that a CHA₂DS-VASc score of 2 would have been considered intermediate or low risk in older guidelines but it was the cutoff for recommending oral anticoagulation in the new guidelines.

“Before we can be sure that adopting one risk scheme over another is really a good thing, it is necessary to consider what the actual net clinical benefit of such a change will be, accounting for strokes prevented and bleeds induced,” she wrote.

The highest risk patients should accrue the most benefit, making oral anticoagulants a reasonable value in this group. “However, because the updated guideline primarily affects people at the lower end of stroke risk, increased anticoagulant use may lead to substantial increases in health care costs with uncertain net clinical benefit,” Fang cautioned.