Warfarin Management Practices and Outcomes in Ambulatory Patients at Kenyatta National Hospital

Abstract

Background: Thrombosis is a major public health problem that is associated with considerable morbidity and mortality. Warfarin is one of the most frequently used oral anticoagulants in Kenya to manage and prevent thrombosis 1. Warfarin safety and efficacy depend on proper dosing, careful monitoring, patient education and maintaining INR within an optimal therapeutic range. Improvement in quality of warfarin management requires understanding of management practices and outcomes which this study set out to explore. Objectives: The objective of this study was to determine the adequacy of anticoagulation control using time in therapeutic range (TTR). The study also aimed to describe warfarin management practices, their association with TTR and to determine the relationship between TTR and thrombotic and bleeding complications in ambulatory patients at Kenyatta National Hospital (KNH). Methods: This study was a retrospective cohort study of warfarin-treated patients in the calendar year 2019 at cardiology, hematology and cardiothoracic clinics at KNH. The study had 2 sources of data; data on INR values, frequency of monitoring and dose adjustment were extracted from patient files and data on knowledge and complications was captured from interviewing patients. All these retrospective data was collected between August 2021 and October 2021. Data analysis was done using SPSS version 23.0. Statistical significance was interpreted at 5% level of significance. Results: We recruited 146 patients. Majority (67.8%) were female with mean age of 46.6 years. Most common indication of warfarin therapy was VTE at 41%. The mean TTR was 43.6% with 71.2% of patients maintaining TTR of <60%. Median monitoring frequency was 73 days. Majority (54.1%) had inappropriate dosage adjustment. Only 19.2% had adequate knowledge on anticoagulation. The most common complication was bleeding at 34.2% while thrombosis occurred in 12.3%. Patients who had poor control were 2.9 times more likely to bleed than those with good control. Patients who had inappropriate dosage adjustment were 2.4 times more likely to have poor anticoagulation control. Conclusion: Majority of patients on warfarin had poor anticoagulation control. Patients had inadequate monitoring frequency and poor knowledge on warfarin. Inappropriate dosage adjustment was a predictor of poor anticoagulation control. Bleeding complications were the most common complication of warfarin therapy and this was significantly associated with poor anticoagulation control.