Abstract: Objective  To explore the value of enzyme-linked immunospot assay （ELISPOT）（ T-SPOT.TB ）in diagnosis of smear-negative pulmonary tuberculosis.  Methods  Rapid T-SPOT.TB assay was employed to detect Mycobacterium tuberculosis antigen specific T cells in blood samples from 55 cases with smear-negative pulmonary tuberculosis(A group) and 36 cases with non-TB pulmonary disease(B group)，The conventional PPD skin test and serum tuberculosis antibody were performed in two groups at the same time.  Results  By the T-SPOT.TB assay，the positive rate in A group was 89.1% (49/55)，it was significantly  higher than that of B group 19.4% (7/36) （χ²=44.59，P<0.001）.In A group，the positive rate of T-SPOT.TB assay was much higher than the positive rate of PPD test and serum tuberculosis antibody and the positive rate of PPD test combination with serum tuberculosis antibody（χ²=12.13，χ²=7.08，χ²=21.54，P<0.01）.In B group，the negative rate of T-SPOT.TB assay was 80.6% (29/36)，it was no significant difference than the negative rate of PPD test and serum tuberculosis antibody  and the negative rate of PPD test combination with serum tuberculosis antibody （χ²=0.39，χ²=0.41，P>0.05）. Conclusion  T-SPOT.TB assay is superior specificity and sensitivity of PPD test and serum antibody. It will be a useful tool to diagnose early smear-negative pulmonary tuberculosis. T-SPOT.TB is worth further to expand in the clinical application.

Key words: Tuberculosis, pulmonary/diagnosis, Immunoenzyme techniques, Tuberculin test