Performance Evaluation of IGRA-ELISA and T-SPOT.TB for Diagnosing Tuberculosis Infection.

BACKGROUND: To explore the application value of IGRA-ELISA in the diagnosis of tuberculosis. METHODS: A total of 68 tuberculosis and 58 other pulmonary disease case samples were obtained. All the samples were tested by IGRA-ELISA and T-SPOT.TB assay in parallel. The consistency of IGRA-ELISA and T-SPOT.TB in the diagnosis of TB was analyzed. Five different methods for the diagnosis of TB were assayed: IGRA-ELISA, T-SPOT.TB, AFB staining, TB-Ab, and PPD. For the different PPD positive degrees, IGRA-ELISA and T-SPOT.TB positive rates were calculated. AFB staining positive and negative samples were analyzed by IGRA-ELISA, T-SPOT.TB, TB-Ab, and PPD. Positive rates, sensitivity, specificity, PPV, NPV and accuracy values of the five different detection methods were compared. RESULTS: There was good consistency between IGRA-ELISA and T-SPOT.TB in the diagnosis of TB and other pulmonary diseases. Compared with T-SPOT.TB, there was a significant correlation between the absorbance value of IGRA-ELISA and the number of ESAT-6 or CFP-10-specific SFCs (r = 0.902, p < 0.001; r = 0.901, p < 0.001). There was a significant difference in the positive rates among the above five different detection methods in the TB group and non-TB group (p < 0.001). For the different PPD positive degrees, there were highly significant differences in the positive rates of IGRA-ELISA and T-SPOT.TB in non-TB group; no similar trend was observed in the TB group. No significant differences in sensitivity, specificity, PPV, NPV, accuracy, LR+ and LR- were observed between IGRA-ELISA and T-SPOT.TB. The positive rates of IGRA-ELISA and T-SPOT.TB in the TB group were significantly higher than that of AFB staining, TB-Ab, and PPD (p < 0.05). IGRA-ELISA and T-SPOT.TB combined with AFB staining could further improve the sensitivity of tuberculosis detection without reducing its specificity. The AUC of IGRA-ELISA, ESAT-6, CFP-10, and T-SPOT.TB were 0.923, 0.893, 0.937, and 0.919, respectively. CONCLUSIONS: There was good correlation and consistency between the IGRA-ELISA and T-SPOT.TB in the diagnosis of TB. The sensitivity and accuracy of IGRA-ELISA were significantly better than those of AFB staining, TB-Ab, and PPD. IGRA-ELISA combined with AFB staining could further improve the diagnosis of tuberculosis.