Diagnostic value of enzyme-linked immunospot assay for diagnosis of smear-negative pulmonary tuberculosis

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,P0.001).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,P0.01).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,P0.05).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.