Adherence to treatment guidelines: the association between stroke risk stratified comparing CHADS2 and CHA2DS2-VASc score levels and warfarin prescription for adult patients with atrial fibrillation

Scott A. Chapman, Catherine A. St Hill, Meg M. Little, Michael T. Swanoski, Shellina R. Scheiner, Kenric B. Ware, M. Nawal Lutfiyya

Ischemic stroke is a risk associated with atrial fibrillation (AF) and is estimated to occur five times more often in afflicted patients than in those without AF. Anti-thrombotic therapy is recommended for the prevention of ischemic stroke. Risk stratification tools, such as the CHADS2, and more recently the CHA2DS2-VASc, for predicting stroke in patients with AF have been developed to determine the level of stroke risk and assist clinicians in the selection of antithrombotic therapy. Warfarin, for stroke prevention in AF, is the most commonly prescribed anticoagulant in North America. The purpose of this study was to examine the utility of using the CHADS2 score levels (low and high) in contrast to the CHA2DS2-VASc when examining the outcome of warfarin prescriptions for adult patients with AF. The CHA2DS2-VASc tool was not widely used in 2010, when the data analyzed were collected. It has only been since 2014 that CHA2DS2-VASc criteria has been recommended to guide anticoagulant treatment in updated AF treatment guidelines. Bivariate and multivariate data analysis strategies were used to analyze 2010 National Ambulatory Care Survey (NAMCS) data. NAMCS is designed to collect data on the use and provision of ambulatory care services nationwide. The study population for this research was US adults with a diagnosis of AF. Warfarin prescription was the dependent variable for this study. The study population was 7,669,844 AF patients. Bivariate analysis revealed that of those AF patients with a high CHADS2 score, 25.1% had received a warfarin prescription and 18.8 for those with a high CHA2DS2-VASc score. Logistic regression analysis yielded that patients with AF had higher odds of having a warfarin prescription if they had a high CHADS2 score, were Caucasian, lived in a zip code where < 20% of the population had a university education, and lived in a zip code where < 10% of the population were living in households with incomes below the federal poverty level. Further, the analysis yielded that patients with AF had lesser odds of having a warfarin prescription if they were ≥ 65 years of age, female, or had health insurance. Overall, warfarin appears to be under-prescribed for patients with AF regardless of the risk stratification system used. Based on the key findings of our study opportunities for interventions are present to improve guideline adherence in alignment with risk stratification for stroke prevention. Interprofessional health care teams can provide improved medical management of stroke prevention for patients with AF. These interprofessional health care teams should be constituted of primary care providers (physicians, physician assistants, and nurse practitioners), nurses (RN, LPN), and pharmacists (PharmD, RPh).