Warfarin Knowledge in Patients with Atrial Fibrillation: Implications for Safety, Efficacy, and Education Strategies

Background: Multiple factors influence warfarin metabolism and can significantly affect the risk of adverse events. The extent to which patients understand the modifiable factors that impact on warfarin safety and efficacy is unclear. Methods: A 52-item questionnaire related to knowledge of warfarin was administered to patients with atrial fibrillation in a face-to-face interview with a dietitian. Results were compiled based on five categories: general warfarin knowledge, compliance, drug interactions, herbal or vitamin interactions, and diet. Results: 100 patients were surveyed. Stroke risk factors included hypertension (57%), heart failure (36%), age >75 years (33%), diabetes (22%), and prior stroke/transient ischemic attack (29%). The majority were either high-school (49%) or college graduates (27%). Ten (10%) had a stroke while on warfarin, 11 (11%) had a blood transfusion, and 26 (26%) had at least one fall. The percentages correct for questionnaire items in the five categories were as follows: general knowledge (62%), compliance (71%), drug interactions (17%), herbal or vitamin interactions (7%), and diet (23%). Neither education level nor duration of therapy correlated with warfarin knowledge. Patients at highest risk of stroke had very low knowledge scores in general. Discussion: Patients on warfarin have a poor general understanding of the medication, particularly those at highest risk of stroke.