Anticoagulation control in a standard of care versus a pharmacist-managed warfarin monitoring service at Windhoek Central Hospital, Namibia
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Date
2024
Authors
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Publisher
University of Namibia
Abstract
Introduction: Warfarin remains the drug of choice for treating thromboembolic
diseases in Namibia. A historical control study reported a patient’s mean time in the
therapeutic range (TTR) at the Warfarin Outpatient Clinic of Windhoek Central
Hospital (WCH) to be suboptimal (29.4%). Interventions to improve anticoagulation
control were instituted and they involved a pharmacist-directed warfarin therapy. The
main objective was to improve anticoagulation control in the intervention group and
compare it to the historical control group.
Methods: A prospective cohort design was used. Adult patients who attended the
warfarin clinic on Wednesdays and gave consent were exposed to the intervention
study. The main outcome measure was the TTR computed using the Rosendaal
method. Binary logistic regression was used to identify factors associated with poor
anticoagulation control. A between groups comparison of anticoagulation control was
based on the paired and unpaired patient cases. A p value < 0.05 was considered
statistically significant. Results: A total of 330 patients were part of the present study
(control (215) and intervention (115)). The majority (63.4%) of the patients in the
intervention group were females. The mean (± SD) age was 45 ± 17 years. The top
three prevalent clinical indications for warfarin in the intervention study were deep
vein thrombosis (49.6%), mitral valve replacement (13.9%), and pulmonary embolism
(13%). Only the baseline INR (OR 0.34 [95%CI: 0.13-0.86]) and warfarin dosage
adherence (OR 0.17 [95%CI: 0.04-0.84]) were significant predictors of good
anticoagulation control in the intervention group. The Mann-Whitney U test showed
an 18% (p<0.050) improvement in the median %TTR when the unpaired cases
between the groups were compared. The paired t-test showed a 10% (p=0.220)
improvement in the mean %TTR when the paired patient cases between the groups
were compared. Conclusion: Interventions involving a pharmacist-directed warfarin
therapy were associated with improved anticoagulation control at the WCH warfarin
clinic. Baseline INR and warfarin dosage adherence were statistically significant
predictors of good anticoagulation control
Description
A thesis submitted in fulfillment of the requirements for the Degree of Master of Pharmacy in Clinical Pharmacy
Keywords
Warfarin, Anticoagulation, Time in therapeutic Range, Pharmacist, University of Namibia, Namibia