Study population and the questionnaire

The study population was composed of patients undergoing warfarin therapy who visited the clinic from September 2015 to June 2017. Inclusion criteria were as follows: 1) patient had received a verbal anticoagulation education and received written educational material before participating in the study; 2) patient had taken warfarin continuously for >3 months to ensure that warfarin had reached the steady state; and 3) patients were able to visit the clinic for each of the 1-month follow-ups and had at least five INR measurements during the 1-year study period.

The AKA questionnaire was selected to assess patients’ warfarin knowledge.8–10 The AKA questionnaire comprises 29 multiple-choice questions related to different aspects of warfarin therapy. The English questionnaire was translated into a Chinese version according to the standard translation procedures.11 The following information was obtained from patients’ medical records: gender, age, educational level, duration of therapy, and diagnosis. Patients who met the inclusion criteria were invited to the study, and those who consented to the study self-completed the questionnaire at the clinic.