Treatment response monitoring in pulmonary tuberculosis: a prospective evaluation of an automated rRNA-based assay

To systematically assess the performance of the advanced TB‑SAT system for tuberculosis therapy monitoring, comparing it with smear microscopy and culture throughout the entire treatment course. This prospective study enrolled confirmed active pulmonary tuberculosis patients at two municipal hospitals from August 2022 to December 2023. Patients were followed during standard anti‑TB treatment, with serial sputum specimens tested by smear microscopy, culture, and the automated TB‑SAT assay. Using culture as the reference standard, we calculated the sensitivity, specificity, and predictive values of TB‑SAT and smear microscopy. Of 283 patients who completed treatment, TB‑SAT consistently showed higher positivity rates than smear microscopy at all time points. Using culture as the reference, TB‑SAT demonstrated significantly higher sensitivity (66.7%‑100%) than smear microscopy (38.9%‑75%) throughout treatment, with specificity increasing from 48.8% at week 2 to 95.7% at end of treatment. Regarding treatment response dynamics, culture achieved the highest negativity conversion rate (92.2%), followed by smear (88.0%) and TB‑SAT (83.1%), whereas smear had the shortest mean time to negativity (27.3 days), followed by culture (35.4 days) and TB‑SAT (57.6 days). Kaplan‑Meier analysis revealed that TB‑SAT exhibited the earliest onset of negative conversion despite its longer mean time to negativity. The automated rRNA‑based TB‑SAT assay exhibits high sensitivity and favorable kinetic characteristics for monitoring treatment response in pulmonary tuberculosis. It outperforms smear microscopy and reflects the decline of metabolically active bacilli.