[The in-vitro interferon-gamma release assay for the diagnosis of tuberculosis and Mycobacterium tuberculosis infections].

OBJECTIVE

To investigate the in-vitro interferon-gamma (IFN-gamma) release assay based on three different Mycobacterium tuberculosis antigens in the diagnosis of tuberculosis and Mycobacterium tuberculosis infections.

METHODS

The peripheral blood mononuclear cells (PBMC) were collected from the patients with tuberculosis (tuberculosis group, n = 57), patients with lung cancer (lung cancer group, n = 29), and healthy controls (healthy control group 2, n = 27). The PBMCs were co-cultured for 5 days with different antigens: purified protein derivatives (PPD) of tuberculin, early secretary antigenic target 6,000 protein (ESAT6) and 38,000 antigen. The protein levels of IFN-gamma were detected by ELISA, and the results were compared to those with the tuberculin skin test (TST).

RESULTS

(1) For healthy controls, the TST was positively related to the history of BCG vaccination and the closeness of contact with sputum-positive tuberculosis patients (P = 0.047, P = 0.041 respectively). The ESAT6 based IFN-gamma release assay was only significantly related to the closeness of contact with sputum-positive tuberculosis patients (P = 0.005), but not to the history of BCG vaccination. (2) There was no significant difference of the TST results among the three groups (P > 0.05). (3) The receiver operating characteristic (ROC) curve analysis indicated that the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the IFN-gamma release assay based on 38,000 antigen were 64.9%, 89.3%, 77.0%, 86.0%, and 71.0% respectively for the diagnosis of tuberculosis.

CONCLUSIONS

IFN-gamma release assay based on ESAT6 appears to be better than TST in the diagnosis of infection of Mycobacterium tuberculosis, while IFN-gamma release assay based on 38,000 may be helpful for the diagnosis of tuberculosis.