Abstract: ObjectiveTo study the value of M.tuberculosis (MTB) DNA(MTB-DNA) in bronchoalveolar lavage fluid (BALF) detected by fluorescence quantitative polymerase chain reaction (FQ-PCR) in diagnosing smear-negative pulmonary tuberculosis.MethodsFQ-PCR was uesd to detect the MTB-DNA in BALF from 300 smear-negative pulmonary TB patients,178 smear-positive pulmonary TB patients and 119 patients with pneumonia or lung cancer.ResultsThe positive rates of MTB-DNA in 3 groups patients mentioned above were 74.3%（223/300）, 94.9%（169/178）, and 17.6%（21/119）, respectively. ConclusionDetecting MTB-DNA in BALF by FQ-PCR could significantly improve the sensitivity of the diagnosis of TB, might become a helpful method for the diagnosis of TB.

Key words: tuberculosis,pulmonary/diagnosis, bronchoalveolar lavage fluid, Mycobacterium tuberculosis, DNA,bacterial, polymerase chain reaction