Assessment of the patient factors impacting on oral anticoagulation therapy among adult outpatients at Kenyatta national hospital

Abstract

Background: Warfarin is indicated for the prophylaxis and treatment of thrombosis. Despite being the oral anticoagulant of choice in many countries, its use is associated with severe side effects notably bleeding and thrombosis. Warfarin has a narrow therapeutic index suggesting that the risk of one developing these complications is quite high if the predisposing factors are not known and measures put in place to counter them. Patients’ knowledge on anticoagulation and other patient factors, just like in most chronic illnesses, may have an impact on anticoagulation control. Objective The objective of this study was to assess the patients’ knowledge on anticoagulation and explore the patient factors affecting anticoagulation control among adult outpatients taking warfarin at Kenyatta National Hospital. Methodology This was a cross-sectional study carried out at the hemato-oncology, cardiac and cardiothoracic clinics of Kenyatta National Hospital during the months of March to May 2015. Adult outpatients taking warfarin who consented to the study were recruited consecutively during the clinic days. A pre-designed structured questionnaire was administered to obtain information from the patients about their knowledge of and adherence to anticoagulation therapy and to identify patient factors that may impact on one’s anticoagulation control. The patients’ INR was also measured. The data was analyzed using the statistical software, SPSS version 20. Results A total of 147 patients completed the study of whom majority (74.1%) were females. The median age [range] was 41[18-74] years. Eighty percent had scores indicative of insufficient knowledge on anticoagulation control (score <75%). Deficiency in knowledge was worst in the aspects of drug and food interactions with warfarin, effect of missing a warfarin dose, interpretation of INR values and recognition of symptoms of over or under dosing warfarin. Adequate knowledge on anticoagulation was statistically significantly associated with marital status (p=0.015), level of education (p=0.014) and indication for oral anticoagulation therapy (p=0.032). Adherence to warfarin and anticoagulation control were low at 52.2% and 43.5% respectively. Independent predictors of poor anticoagulation were female gender (p=0.011) and lower education level (p=0.005). Patient knowledge on anticoagulation and adherence to warfarin were not statistically significantly associated with anticoagulation control (p=0.794) and (p=0.834). Conclusion Knowledge on and adherence to anticoagulation therapy in patients on warfarin at KNH is poor. The level of anticoagulation control is inadequate. Female gender and lower education level were predictors of poor anticoagulation. Knowledge on anticoagulation was however not associated with anticoagulation control. Recommendations Further larger studies incorporating all the variables that can affect anticoagulation control should be conducted at KNH to identify the causes of inadequate anticoagulation control.