Factors associated with extended treatment duration in patients with drug-susceptible pulmonary tuberculosis: a prospective multicentre cohort study in South Korea.

BACKGROUND

The standard treatment for drug-susceptible tuberculosis (TB) is a 6-month short-course regimen; however, extended courses are often used in clinical practice. We aimed to identify factors associated with extended treatment in patients with drug-susceptible TB.

METHODS

We conducted a prospective cohort study across 18 institutions in the Republic of Korea between July 2019 and June 2023 and enrolled patients with drug-susceptible TB who received the standard short-course regimen (isoniazid, rifampin, pyrazinamide, and ethambutol) and achieved treatment success at end of therapy. Patients were categorised by treatment duration: less than 200 days (standard treatment group) and more than 200 days (extended treatment group).

RESULTS

Of 854 patients, 334 (39.1%) received extended treatment, and 520 (60.9%) received standard treatment. Baseline characteristics differed between groups (extended vs. standard): diabetes mellitus (31.4% vs. 22.5%; P = 0.01), a history of TB treatment (22.2% vs. 10.4%; P < 0.01), multilobar involvement (47.2% vs. 34.3%; P < 0.01), cavitary lesions on chest radiography (32.1% vs. 12.5%; P < 0.01), acid-fast bacillus (AFB) smear positivity (38.9% vs. 14.2%; P < 0.01), gastrointestinal adverse reactions (48.8% vs. 41.9%; P < 0.05), and treatment interruption > 7 days (11.1% vs. 3.1%; P < 0.01). In weighted logistic regression, previous TB (odds ratio [OR] 2.66, 95% confidence interval [CI] 1.67–4.25; P < 0.01), cavity (OR 2.56, 95% CI 1.63–4.02; P < 0.01), and AFB smear positivity (OR 4.06, 95% CI 2.73–6.04; P < 0.01) were significant baseline predictors of extended treatment. In the time-updated Cox analysis, older age (adjusted hazard ratio [aHR] 0.84, 95% CI 0.75–0.95; P < 0.01) and lower body mass index (aHR 0.95, 0.90–0.99; P = 0.02) were associated with a decreased likelihood of extended treatment. In contrast, cardiovascular disease (aHR 1.20, 1.06–1.36; P = 0.01), chronic lung disease (aHR 1.10, 1.01–1.19; P = 0.03), chronic kidney disease (aHR 1.15, 1.01–1.31; P = 0.03), malignancy (aHR 1.16, 1.03–1.30; P = 0.01), previous TB (aHR 1.09, 1.02–1.15; P = 0.01), and cavity (aHR 1.06, 1.01–1.12; P = 0.03) were positively associated with extended treatment. Among time-dependent factors, leucopenia (aHR 1.08, 1.02–1.16; P = 0.02) and 2-month culture positivity (aHR 1.09, 1.01–1.18; P = 0.03) were associated with an increased likelihood of extended treatment, whereas neuropathy (aHR 0.89, 0.80–0.98; P = 0.02) and nephrotoxicity (aHR 0.89, 0.80–0.98; P = 0.02) were associated with a decreased likelihood.

CONCLUSION

This study identified patient and treatment factors associated with extended therapy for drug-susceptible TB in the Republic of Korea, underscoring the need for targeted interventions and strengthened monitoring to optimise treatment outcomes. CLINICAL TRIAL: This study was registered with the Clinical Research Information Service (CRIS), Republic of Korea (https://cris.nih.go.kr, registration number KCT0002594) on 1 November 2017.