Adverse clinical outcomes of warfarin therapy and predictors among adult outpatients at public hospitals in Nekemte town, western Ethiopia: A retrospective cross-sectional study

Background Management with warfarin therapy becomes challenging globally due to the increased risk of adverse clinical outcomes from its use. In Africa, warfarin-related bleeding events and thromboembolic complications range from 0.006 % to 59 % and 1.6 %–7.5 %, respectively. Objectives This study aimed to determine adverse clinical outcomes of warfarin therapy and predictors among adult outpatients at Wallaga University Referral and Nekemte Comprehensive Specialized Hospitals from April 1, 2021 to March 31, 2023. Methods An institutional-based retrospective cross-sectional study was conducted from June 1 to July 31, 2023, by reviewing the patient's medical charts with warfarin indications. Descriptive statistics such as frequencies, percentages, means, and standard deviations were computed. Bivariable and multivariable logistic regression analyses were performed to check the association between dependent and independent variables. In multivariable logistic regression analysis, an adjusted odds ratio (AOR) with 95 % CI was determined and statistical significance was declared at a p-value <0.05. Results A total of 402 patients' medical charts with warfarin indications were reviewed. The mean age of the study participants was 38.9 ± 17.9 years and 271(67.4 %) were female patients. Bleeding events 19(4.7 %) and thromboembolic complications 32(8 %) were adverse clinical outcomes of warfarin therapy observed in this study. Warfarin therapy used for 4–6 months (AOR = 3.270; [CI: 1.043–10.252]; p-value = 0.042), hypertension comorbidity (AOR = 3.582; [CI: 1.015–12.642]; p-value = 0.047) and aspirin use (AOR = 5.043; [CI: 1.964–12.948]; p-value = 0.001) were the independent predictors of warfarin related bleeding events. Patients aged 41–64 years were 67.4 % less likely to develop warfarin-related thromboembolic complications than those patients aged 18–40 years (AOR = 0.326; [CI: 0.108–0.983]; p-value = 0.046). Conclusions Adverse clinical outcomes were found to be observed in less than one-fourth of the study participants in our study. Warfarin use for 4–6 months, hypertension comorbidity, and concomitant use of aspirin were identified as the independent predictors of warfarin-related bleeding events. The age range of 41–64 years was less likely predictive of warfarin-related thromboembolic complications. Institutional-based guidelines and clinical pharmacist involvement in anticoagulation management play a vital role in preventing adverse clinical outcomes.