The effect of warfarin knowledge on anticoagulation control among patients with heart valve replacement

Background Although novel oral anticoagulants have been applied into clinical practice, warfarin remains the only approved oral anticoagulant for heart valve replacement. Currently, an increasing number of Chinese clinical pharmacists provide patients with warfarin education. However, little research to date has been carried out to evaluate the relationship between warfarin knowledge level and anticoagulation control among patients with heart valve replacement. Objective To evaluate knowledge of warfarin and the relationship between knowledge level and anticoagulation control among patients with heart valve replacement. Setting Fujian Medical University Union Hospital, China. Method A prospective and cross-sectional study was designed to evaluate the warfarin education of inpatients new to warfarin therapy using a validated Anticoagulation Knowledge Assessment questionnaire. Included patients were followed up for at least 3 months. Data were retrieved from hospital databases and telephone follow up. Main outcome measure Spearman's rho correlation analysis was used to assess the relationships between time in therapeutic range and warfarin knowledge level. Results 383 patients were included. The mean age of patients was 50.3 ± 7.9 years. The mean knowledge questionnaire score was 62.3 ± 8.8%. The majority of incorrect answers related to drug-warfarin interaction. Five of the frequently incorrect questions covered drugs, herbs and diet that affect warfarin therapy. There were significant correlations between total questionnaire score and time in therapeutic range (rho = 0.539, P < 0.001), or percentage of international normalized ratio measurements within range (rho = 0.416, P < 0.001). There were significant correlations between patients' educational level and total questionnaire score (rho = 0.357, P = 0.001). No significant correlations were found between income or living area and total questionnaire score (rho = 0.110, P = 0.435; rho = 0.161, P = 0.149). Conclusion Patient knowledge level of anticoagulation therapy affects anticoagulation control. Education for patients new to warfarin and the evaluation of knowledge by validated questionnaire is recommended for better INR control.