Prevalence and Factors Associated with Non-Adherence to Warfarin Treatment: A Single Center Study in Sri Lanka

Introduction: Warfarin is a prescription oral anticoagulant that has a narrow therapeutic index. This study was conducted to assess the prevalence and the associated factors of non-adherence to Warfarin treatment.Methodology: A cross-sectional study was conducted among a sample of 282 patients who are on warfarin and attending haematology and general medical clinics at a Tertiary care hospital in Sri Lanka. Adult patients who had started warfarin treatment 3 months ago with a clear diagnosis of warfarin indication were included in the study. Adherence was measured using the modified Morisky Medication Adherence Scale (MMAS-8). The Oral Anticoagulation Knowledge test (OAK) was used to assess knowledge.Results: Nearly 40% had insufficient knowledge of warfarin. The prevalence of non-adherence was detected as 57.8%. Patients who had unsatisfactory knowledge of warfarin were more likely to have non-adherence to warfarin treatment (OR 15.58, 95% CI 8.05-30.16, p<0.001). None of the sociodemographic or treatment-related factors were associated with non-adherence.Conclusion and recommendations: Patients who had unsatisfactory knowledge of warfarin were more likely to have non-adherence to warfarin treatment, interventions will be required to increase knowledge of warfarin among patients who are on warfarin.