Quality of Oral Anticoagulation Management Among Patients on Follow Up at Kenyatta National Hospital

Abstract

Background: Oral anticoagulation with warfarin for various indications is challenging given that it has a narrow therapeutic index. Quality management of patients on warfarin is therefore important to minimize the complications of bleeding and thrombosis associated with warfarin therapy. Published literature on the quality of oral anticoagulation management in Kenyatta National Hospital is scanty hence this study sought to fill this gap. Objective: The objective of this study was to describe the quality of oral anticoagulation among patients who are on follow-up at Kenyatta National Hospital. Methods: A retrospective cross-sectional study design which analyzed data for eligible participants treated between January 2014 and June 2016 was carried out at Kenyatta National Hospital. Four hundred and six files of all age-groups of patients on warfarin anticoagulation who met the study inclusion criteria were reviewed. A pre-designed structured data collection form was used to extract data from patient files on socio-demographics, indications and duration of warfarin therapy, comorbidities, concomitant medicines and International Normalized Ratio values and the dates the tests were taken. The percentage of follow-up time spent in therapeutic range was computed by Rosendaal Linear Interpolation method. The data was analyzed using IBM Statistical Package for Social Sciences version 22.0. Multivariate linear regression was used to identify independent predictors of poor anticoagulation control. Statistical significance was determined at 95% confidence level. Results: Female to male ratio was 3:1 and the mean age of the study population was 43 years. Venous thromboembolism was the main indication for warfarin use. Percentage of time spent in therapeutic anticoagulation control was 31.1% and a fifth of the patients had therapeutic International Normalized Ratio for 50% or more of their follow-up time. The median frequency of monitoring was 18.5 days [interquartile range 9.5-34.7]. Proportion of time that International Normalized Ratio was in therapeutic range was associated with renal dysfunction (β = -13.3, p = 0.038). Independent predictors of time outside therapeutic levels were deep venous thrombosis (β= 15.0, p < 0.001), atrial fibrillation (β= 17.0, p = 0.001), prosthetic valves (β = 27.7, p < 0.001), the use of corticosteroids (β= 18.2, p = 0.026), Islam religion (β = 21.2, p = 0.013) and lower education level (β=5.5, p = 0.037). Congestive heart failure was associated with poor anticoagulation control (p=0.047) whereas valvular heart disease and long duration of anticoagulation were predictors of decreased frequency of monitoring (β =8.6, p = 0.042 and β = 18.0, p<0.001 respectively). Conclusion: The quality of oral anticoagulation with warfarin in Kenyatta National Hospital is poor especially among patients with renal dysfunction, congestive heart failure and concomitant therapy suggesting that better management and monitoring of patients with these conditions need to be emphasized. Larger studies to determine the reasons for the poor quality and find association between time in therapeutic range and outcomes of warfarin therapy should be conducted.