Role of QuantiFERON-TB Gold antigen-specific IL-1β in diagnosis of active tuberculosis.

The main objective of the study was to evaluate whether in vitro QuantiFERON-TB Gold In-Tube (QFT-GIT) assay antigen-specific IL-1β, TNF-α, IL-2, IL-6, IL-8 and IL-12 (p40) production is associated with active TB. In a cohort of 77 pulmonary TB patients (PTB), 67 healthy household contacts (HHC) and 83 healthy control subjects (HCS), the antigen-specific cytokines levels were determined in supernatants generated from QFT-GIT tubes. Antigen-specific IL-1β levels were significantly higher in PTB than HHC and HCS. At a fixed cutoff point (1,108 pg/ml), IL-1β showed positivity of 62.33% in PTB, 22.38% in HHC and 22.89% in HCS. Moreover, antigen-specific IL-1β assay can differentiate PTB and HHC (believed to be latently infected) (p < 0.0001). Like IL-1β, significantly higher levels of antigen-specific TNF-α were associated with PTB and displayed 43.63% positivity in PTB. The antigen-specific IL-2 levels were associated both with PTB (54.54%) and HHC (48.14%). Other cytokines levels did not differ among the groups. Our results suggest that antigen-specific IL-1β can be used as a biomarker for active TB diagnosis as well as for differential diagnosis of PTB and LTBI.