Impact of adherence, knowledge, and quality of life on anticoagulation control

BACKGROUND: Patients receiving chronic warfarin therapy who have poor anticoagulation control are at increased risk for adverse events. However, it is unknown how adherence to warfarin, patient demographics, patient knowledge about therapy, and perceived impact of warfarin therapy on quality of life are associated with anticoagulation control. OBJECTIVE: To determine the association between these patient factors and anticoagulation control in patients attending 2 anticoagulation clinics in the Bronx, New York City. METHODS: A cross-sectional survey of 52 patients was conducted. The 4-item Morisky survey was used to assess self-reported adherence. Patient knowledge about warfarin therapy and the perceived impact of warfarin therapy on quality of life were determined by self-administered questionnaires. Associations between adherence, patient knowledge, impact of warfarin therapy on quality of life, and anticoagulation control were determined with (-tests, χ ² analysis, and logistic regression. RESULTS: Only 14% of patients had good anticoagulation control. Adequate adherence was reported by 50% of patients and was significantly associated with good anticoagulation control (p = 0.01). Thirty-seven percent of participants had good knowledge of anticoagulation, and 19% of participants reported that warfarin negatively impacted their quality of life. Knowledge about warfarin therapy and impact of warfarin on quality of life were not significantly associated with anticoagulation control. CONCLUSIONS: Adherence is one of many factors that contribute to anticoagulation control. Adequate adherence, as determined by the Morisky survey, was significantly associated with anticoagulation control. Patient demographic characteristics, knowledge about warfarin therapy, and perceived impact of warfarin on quality of life were not associated with anticoagulation control.