A preliminary study on the clinical value of simultaneous amplification and testing for tuberculosis (SAT-TB) for early therapeutic monitoring in multidrug-resistant/rifampicin-resistant tuberculosis

Multidrug-resistant/rifampicin-resistant tuberculosis (MDR/RR-TB) poses a major global health challenge due to its complex treatment regimen and the lack of rapid and effective monitoring tools. Conventional methods, such as the long-culture-period MGIT™960 and molecular assays like Xpert, which cannot distinguish between viable and nonviable bacteria, are unable to meet the clinical demand for dynamic monitoring. A total of 125 patients with MDR/RR-TB diagnosed at Hangzhou Red Cross Hospital between January 2022 and October 2024 were included in the study. Sputum samples were collected at baseline (T0), the end of the 1st month of treatment (T1), and the end of the 2nd month of treatment (T2). Samples were tested using sputum simultaneous amplification and testing for tuberculosis (SAT-TB), acid-fast staining (AFS), and MGIT™960 culture. With MGIT™960 culture serving as the gold standard, the diagnostic performance of SAT-TB and AFS was evaluated in terms of sensitivity, specificity, and consistency using Kappa values and receiver operating characteristic curve analysis. At T0, the sensitivity of sputum SAT-TB and AFS was 81.6% and 55.2%, respectively. At T1, SAT-TB demonstrated a sensitivity of 87.1% and specificity of 100.0% compared to 54.8% sensitivity and 98.9% specificity of AFS. Kappa values were 0.910 (SAT-TB) and 0.626 (AFS), with significant statistical differences (P < 0.05). Positive predictive values (PPV) were 100% and 94.4%, while negative predictive values (NPV) were 95.9% and 86.9% for SAT-TB and AFS, respectively. The area under the curve (AUC) values were 0.935 for SAT-TB and 0.769 for AFS, with a significant statistical difference (P = 0.0006). At T2, SAT-TB and AFS sensitivities declined to 25.0% and 16.7%, respectively, with respective specificities of 100.0% and 98.2%. The corresponding Kappa values were 0.376 and 0.212, with significant statistical differences (P < 0.05). PPVs were 100% and 50%, and NPVs were 92.6% and 91.7%. The AUC values dropped to 0.625 for SAT-TB and 0.574 for AFS, with no statistically significant difference (P = 0.2305). Sputum SAT-TB demonstrated superior sensitivity and specificity than AFS. At T1, it showed high consistency with MGIT™960 culture, suggesting that sputum SAT-TB is a promising tool for early therapeutic efficacy evaluation in MDR/RR-TB.