Evaluation of Anticoagulation Outcome among Patients Taking Warfarin: A Single-Center Experience, Northwest Ethiopia

Abstract BackgroundWarfarin is a widely used oral anticoagulant in clinical practice. It is used to prevent arterial emboli in patients with atrial fibrillation, or prevent and treat venous thromboembolism. The efficacy and safety of warfarin depends on maintaining the INR within the therapeutic range. The proportion of time spent in the therapeutic INR range (TTR) is used to evaluate quality of anticoagulation control.MethodsA hospital-based cross sectional study was conducted between November 1, 2019 and October 31, 2020 at Cardiac and Hematology Clinic, University of Gondar hospital. A consecutive sampling method was used to recruit 338 study subjects. Proportion of time spent in the therapeutic range (TTR) was calculated using the Rosendaal’s linear interpolation method. TTR ≥65% was described as ‘optimal’ International Normalized Ratio (INR) control. The Data were entered into EPI Info version 4.4.1 and transported to SPSS version 20 for analysis. Logistic regression analysis was used to identify associated factors with optimal anticoagulation outcome (TTR ≥65%). P-values <0.05 were used to declare significant association.ResultA total of 338 study subjects were included in the study. The mean age of patients was 49 years. The majority of study participants attended formal education (79%) and were urban dwellers (57%). Atrial fibrillation was the commonest indication for warfarin therapy. One-third (33%) of study subjects achieved the desired INRs (INR=2.0-3.0), while about one-tenth (13%) of patients attained optimal INR control (TTR≥65%). There were no significant association of socio-demographic characteristics including age, gender, educational level and monthly income with optimal INR control (TTR ≥65%). Likewise, clinical characteristics including dose of warfarin, warfarin adherence, frequency of INR determination, other concomitant drug intake, co-existing comorbidities, consumption of green leafy vegetables and alcohol intake didn’t show significant association with optimal INR control (TTR≥65%).ConclusionInstitution-based validated protocol might be required to overcome the poor TTR level. ‘Anticoagulation (INR) clinic’ would be required to ‘scale-up’ INR control.