Clinical application of T-SPOT.TB assay in tuberculosis diagnosis

Abstract

Objective To investigate the diagnostic value of enzyme-linked immunospot assay for tuberculosis (T-SPOT.TB) in pulmonary tuberculosis and non-pulmonary tuberculosis, and evaluate the clinical application value of T-SPOT.TB's spot forming cell frequencies in the diagnosis of tuberculosis. Methods T-SPOT.TB, tuberculin test (PPD) assay, and tuberculosis antibody test (TB.AB) were used in the diagnosis of tuberculosis among 78 active pulmonary tuberculosis patients, 58 active non-pulmonary tuberculosis patients, 27 old pulmonary tuberculosis patients, and 76 non-tuberculosis patients. Results ⑴ The sensibility and specificity if T-SPOT.TB assay were 71.17% and 78.95%, the highest among 3 methods. Three trials's joint detection obviously increased the sensitivity of tuberculosis diagnosis. ⑵ The positive rate of T-SPOT.TB and spot forming cell frequencies in active pulmonary tuberculosis and active non-pulmonary tuberculosis were not statistically significant (P>0.05). The positive rate of T-SPOT.TB in active pulmonary tuberculosis and old pulmonary tuberculosis were not statistically significant (P>0.05). However, spot forming cell frequencies of T-SPOT.TB in active pulmonary tuberculosis were significantly higher than old pulmonary tuberculosis (P<0.05). ⑶ When spot forming cell frequencies of T-SPOT.TB. of peripheral blood mononuclear cell (PBMC) was set to 11.5 spots-forming cell (SFC)/106 PBMC, it had the best cut-off value to diagnose the tuberculosis as a diagnostic criteria. ⑷ When spot forming cell frequencies of T-SPOT.TB of PBMC was set to 17 SFC/106PBMC, it had the best cut-off value to distinguish the active pulmonary tuberculosis from old pulmonary tuberculosis. Conclusions The joint detection of T-SPOT.TB assay, PPD assay and TB.AB assay, could obviously improve the positive rate of TB infection. T-SPOT.TB assay has useful diagnostic value for pulmonary tuberculosis and non-pulmonary uberculosis. Reasonable application of spot forming cell frequencies contributes to the early diagnosis and treatment of tuberculosis. Key words: Immunoassay; Tuberculosis/DI