Anticoagulation for Patients with Atrial Fibrillation in Ambulatory Care Settings

BACKGROUND: In the context of recently published guidelines, we studied anticoagulation for atrial fibrillation as part of stroke prevention. METHODS: The National Center for Health Statistics ambulatory care surveys use a multistage random sampling design consisting of 112 US geographic primary sampling units, nonfederal physician offices and hospital outpatient departments within those units, and patient visits to those offices and outpatient departments. Patient and visit characteristics were abstracted from 1771 medical records of patients with atrial fibrillation aged 20 years or older from 2001 to 2006, representing a national estimate of 6.1 million annual visits. The dependent variable was the prescription of warfarin. Independent variables included embolic risk factors, age, sex, race, payment source, region, urban-rural location, year, primary care provider status, number of visits during the past year, and documentation of aspirin. Chi2 and logistic regression measured associations with the prescription of warfarin. Analysis was performed in SUDAAN version 9.0 (RTI International, Research Triangle Park, NC). RESULTS: Among patients with atrial fibrillation, warfarin was prescribed during 52.2% of visits. Warfarin use was more likely in 2005 to 2006 than in 2001 and at visits covered by Medicare than by those covered by private insurance. Women and non-white patients were less likely to receive warfarin than their counterparts. Patients taking aspirin were less likely to get warfarin, but there were no significant differences because of age or the presence of risk factors. Warfarin use was more likely in the Northeast as compared with all other regions of the country. CONCLUSIONS: Accepted guidelines for warfarin have been implemented during more than half of visits of patients with atrial fibrillation. Disparities exist among race, sex, and region. More attention is needed to appropriate prescribing of warfarin.