Abstract: Objective T-SPOT.TB is a new method to diagnose tuberculous infection through detecting the frequencies of IFN-γ producing T cells which respond to the M.tuberculosis specific antigens encoded by the RD1 region(ESAT-6 and CFP-10). This study aimed to evaluate the role of T-SPOT.TB in the differentiation of the sarcoidosis and tuberculosis. Methods The data of T-SPOT.TB of 44 sarcoidosis and 30 pulmonary tuberculosis patients in PUMCH between January 2008 and March 2011 were analysed. Results Among the 44 sarcoidosis patients ,the T-SPOT.TB result was positive in 12 patient (27.3%) ,while among the 30 pulmonary tuberculosis patients ,the T-SPOT.TB result was positive in 27 patient (90%) .Pooled frequencies of ESAT-6 and CFP-10 specific IFN-γ secreting T cell was 46SFCs/106PBMC（IQR 28～204） for sarcoidosis patients ,significantly lower than that for pulmonary tuberculosis patients which was 565 SFCs/106PBMC（IQR 170～2340）. Conclusion T-SPOT.TB may be a new method for the differentiation of sarcoidosis from pulmonary tuberculosis.

Key words: [Key words]：Sarcoidosis, Pulmonary tuberculosis, Differential diagnosis, ELISPOT, T-SPOT.TB