Factors Affecting Warfarin-Related Knowledge and INR Control of Patients Attending Physician- and Pharmacist-Managed Anticoagulation Clinics

Abstract

Objectives: To assess the anticoagulation knowledge and international normalized ratio (INR) control among patients on warfarin. Methods: A cross-sectional study with 156 randomly sampled patients from physician- (non-medication therapy adherence clinic [non-MTAC]) and pharmacist (MTAC)-run anticoagulation clinics using a validated interviewer-administered questionnaire. Patients' INR readings from 2008 to 2010 were recorded. Results: Patients on warfarin scored an average of 66.5% ± 36.0% for their knowledge on how warfarin works, 42.9% ± 44.9% for interaction between warfarin and alcohol, and 49.2% ± 21.1% for adverse effects. No significant differences were found between MTAC and non-MTAC patients on their knowledge. There was a negative correlation between patients' knowledge and age ( P = .001, rs = −.293) and a positive correlation between patients' knowledge and education level ( P = .001, rs = .365). MTAC patients were found to have better INR control than non-MTAC when compared for mean percentage days in range (63.4% ± 18.9% vs 52.5% ± 18.2%; P = .006) and mean percentage visits in range (58.8% ± 17.9% vs 46.8% ± 18.6%; P = .001). Conclusions: MTAC patients were found to have better INR control compared to non-MTAC patients. A joint cooperation between physicians, pharmacists, and nurses should exist to achieve desired therapeutic outcomes.