Abstract: Objective To study the diagnostic value of SAT-TB（simultaneous amplification and testing for Mycobacterium tuberculosis） for smear-negative pulmonary tuberculosis(PTB) by testing bronchoalveolar lavage fluid (BLAF). Methods From June 2012 to June 2014 in Shanghai Pulmonary Hospital Tongji University, we screened 252 suspected PTB patients with 3 consecutive negative sputum smears, and obtained their BLAF specimen by brochchoscopy. BALF was tested by both Bactec MGIT 960 culture and SAT-TB assay. We diagnosed all patients, followed up for at least 6 months and collected associated information of patients regarding final diagnosis, culture results, imaging changes. The sensitivity, specificity, PPV and NPV for each diagnostic test were calculated using culture results as reference standard.  Results Of 234 PTB suspects included in the final analysis, 58 were TB culture positive, 112 were PTB patients by clinical diagnosis with culture negative, 64 were non-TB patients. Using culture confirmed results as reference standard, the sensitivity, specificity, positive predictive value, negative predictive value of SAT-TB for smear-negative PTB testing BALF were 81.0%(47/58, 95%CI：69.0%－90.1%), 96.9%(62/64，95%CI：88.9%－100.0%), 95.9% (47/49，95%CI：86.4%－100.0%) and 84.9%(62/73, 95%CI：75.3%－92.2%). The detection time of SAT-TB was around two hours, remarkably shorter than 31 days needed by culture.  Conclusion SAT-TB can provide reliable, fast diagnostic evidence for smear- negative PTB and is a valuable diagnostic method.

Key words: Tuberculosis, pulmonary/diagnosis, Bronchoalveolar lavage fluid, Nucleic acid amplification sechniques