Abstract: Objective To evaluate the value of interferon gamma release assays for the differential diagnosis between pulmonary tuberculosis and lung disease of non-tuberculous mycobacteria (NTM).  Methods We chose 334 cases of pulmonary disease admitted in the Third People’s Hospital of Shenzhen during the period from Februa-ry 2011 to May 2013. Three hundred and thirty-four sputum specimens from these patients were identified by PCR-reverse dot blot hybridization assay. An in-house ELISPOT assay was used to determine Mycobacterium tuberculosis antigen-specific IFN-γ production in patients; PCR-fluorescent probe was used to detect Mycobacterium tuberculosis DNA in sputum specimens (fluorescent quantitative PCR).   Results Of 334 cases, 240 cases were identified as Mycobacterium tuberculosis infection and 94 were identified as non-tuberculosis mycobacteria infection. The positive rate of fluorescent quantitative PCR and IGRAs were 74.58%（179/240）and 77.08%（185/240）, respectively in patients with PTB,while 10.64%（10/94） and 20.21%（19/94）,respectively in patients with lung disease of non-tuberculosis mycobacteria. The sensitivity of the fluorescent quantitative PCR and IGRAs were 74.58%（179/240）and 77.08%（185/240）, respectively; while the specificity of the two methods were 89.36%（84/94）and 79.79%（75/94）, respectively. The sensitivity and specificity of two methods combined were 93.75%（225/240）and 77.66%（73/94）, respectively.  Conclusion IGRAs can detect rapidly and differentiate pulmonary tuberculosis from lung disease of non-tuberculosis mycobacteria, and the accuracy of differential diagnosis can be improved significantly when IGRAs combined with PCR, which is important to select antituberculosis drugs for patients.

Key words: Tuberculosis, pulmonary/diagnosis, Mycobacterium infactions, nontuberculous, Interferon-gamma release tests, Diagnosis, differential