Predictors of Prolonged Treatment in Patients With Drug-susceptible Pulmonary Tuberculosis in South Korea: A Multi-center Registry Analysis From Republic of Korea

Abstract Rationale: The standard treatment for drug-susceptible tuberculosis (TB) typically involves six months of short-course chemotherapy. However, in real-world practice, prolonged treatment is frequently employed. This study aims to identify predictors of prolonged treatment among patients with drug-susceptible TB. Methods: A retrospective analysis was conducted on data from a prospective cohort study carried out between July 2019 and June 2023, involving TB patients from 18 institutions across South Korea. The study aimed to identify risk factors associated with treatment durations exceeding six months in patients with drug-susceptible TB. Results: Among 994 patients with drug-susceptible TB, 588 received standard treatment, while 406 underwent prolonged treatment. The prolonged treatment group had higher rates of diabetes (46.5% vs. 36.0%, p<0.01), retreatment (22.4% vs. 11.4%, p<0.01), multilobar involvement (46.3% vs. 36.7%, p<0.01), and pulmonary cavity (43.8% vs. 19.4%, p<0.01). This group also had higher rates of positive acid-fast bacilli (AFB) smear (46.6% vs. 22.6%, p<0.01), cytopenia during TB treatment (16.3% vs. 11.1%, p=0.02), and treatment interruptions (> 7 days) (14.0% vs. 6.0%, p<0.01). Treatment success was higher in the prolonged group (97.8% vs. 90.5%, p<0.01), with no significant differences in relapse rates (2.5% vs. 2.3%, p=0.79). Binary logistic regression revealed that retreatment (OR = 1.75, CI 1.04-2.95, p=0.03), pulmonary cavity (OR = 2.68, CI 1.70-4.23, p<0.01), positive AFB smear (OR = 3.31, CI 2.16-5.07, p<0.01), treatment interruption (OR = 2.36, CI 1.19-4.67, p=0.01), and cytopenia during TB treatment (OR = 2.01, CI 1.16-3.48, p=0.01) were significant predictors of prolonged treatment. Conclusion: This study establishes that retreatment, pulmonary cavitary, positive AFB smear, treatment interruption exceeding a week, and cytopenia during TB treatment are key factors of a prolonging treatment. These findings underscore the need for targeted interventions and enhanced monitoring to optimize outcomes and minimize adverse events.