Abstract: Objective  To evaluate the diagonsis value of  M.tuberculosis  DNA detected by fluorescence quantitative polymerase chain reaction(FQ-PCR) in sputum and bronchoalveolar lavage fluid(BALF) for patients with smear-negative suspicious pulmonary tuberculosis(PTB). Methods  Fifty one suspicious lung tuberculosis patients from  July to December in 2009 with at least three times negative sputum smear are divided into two groups: 24 cases with suspicious radiological features of pulmonary tuberculosis (suspicious PTB group) and 27 cases with radiological features of non-tuberculosis (excluding PTB group). All of patients underwent tuberculin skin test, anti-TB antibody and erythrocyte sedimentation rate(ESR) are detected, Mtb-DNA of sputum and BALF are detected qualitatively and quantitatively by FQ-PCR. Results  Sputum specimens PCR has a sensitivity of 45.8%（11/24）, specificity of 96.3%（26/27）, and Youden’s index of 42.1%, whereas in BALF specimens, the sensitivity and Youden’s index are significantly higher at 75.0%（18/24）and 71.3% respectively, while the specificity is still high at 96.3%（26/27）. Conclusion  Detecting Mtb-DNA in BALF by FQ-PCR is more sensitive than sputum specimens, and has a good diagnostic yield in patients with suspicious radiological features and sputum smear-negative pulmonary tuberculosis, especially without sputum production.

Key words: Tuberculosis,pulmonary/diagnosis, Mycobacterium tuberculosis, DNA,bacterial, Bronchoalveolar lavage fluid, Sputum