Treatment outcomes and associated factors among patients with drug-resistant tuberculosis in Ethiopia: A retrospective cohort study

• Unsuccessful treatment outcomes occurred in 20.9% of DR-TB patients. • Age 45 years or older was independently associated with poor treatment outcome. • Underweight status increased the odds of unsuccessful outcomes. • Previous loss to follow-up was strongly associated with unsuccessful outcome. • HIV is associated with poor outcomes with consistent effect in sensitivity analysis. Drug-resistant tuberculosis (DR-TB) remains a major public health challenge globally. Despite diagnostic advances and expanded access to all-oral regimens in Ethiopia, treatment outcomes continue to vary across the country. Evidence on factors affecting treatment outcomes under programmatic setups is needed to inform targeted interventions. This study aimed to assess the treatment outcomes and associated factors of DR-TB patients at Adama Hospital Medical College from January 2016 G.C to December 2024 G.C. We conducted a retrospective cohort study among patients treated for DR-TB. Treatment outcomes were classified according to the WHO definitions as successful (cured/completed) or unsuccessful (treatment failure/death/loss to follow-up). Sociodemographic, behavioral and clinical characteristics were extracted from routine records using an online form administered via Kobo Toolbox. The dataset was later exported in CSV format and analyzed using R statistical software (Version 4.3.2). Descriptive statistics were used to summarize the characteristics of the study population. Bivariate logistic regression was initially performed. Variables with a p-value < 0.25 in the bivariate analysis were included into a multivariable Firth penalized logistic regression model addressing sparse data and separation to identify independent predictors of treatment outcomes. Statistical significance was determined at p < 0.05 with a 95% confidence interval. Sensitivity analysis used a model controlling for collapsed regimen categories. Among 249 eligible MDR/RR-TB patients, 197 (79.1%) achieved successful treatment outcomes, while 27 (10.8%) died and 22 (8.9%) were lost to follow-up, while 3 (1.2%) were treatment failures. Of the 249 patients included in the cohort, 238 were included in the multivariable analysis due to complete data availability. In the complete-case analysis using multivariable Firth model (n=238), age ≥45 years was independently associated with an unsuccessful outcome (adjusted odds ratio [AOR] 3.43, 95% CI 1.23-9.89). Underweight patients at enrollment (AOR 2.47, 95% CI 1.19 - 5.36) had increased odds of unsuccessful treatment outcome. Previous defaulters (loss to follow-up) had substantially higher odds of unsuccessful outcome compared to new patients (AOR 7.13, 95% CI 1.02 - 84.26), although confidence intervals were wide due to sparse data. HIV co-infection was associated with increased odds of unsuccessful treatment outcome in the primary analysis (AOR 3.20, 95% CI 1.04 - 10.21). In the sensitivity analysis, the association remained in the same direction, but with borderline significance (AOR 3.01, 95% CI 0.97-9.62). Despite high overall treatment success, older adults, undernourished, and previous defaulters remain at substantially increased risk of unsuccessful DR-TB treatment outcomes. HIV co-infection was also associated with unsuccessful treatment outcomes, with a directionally consistent association in sensitivity analysis. Targeted adherence support, strengthened TB/HIV integration, and improved programmatic monitoring are essential to further reduce mortality and loss to follow-up.