In vitro QuantiFERON-TB gold antigen specific interleukin-1beta to diagnose TB among HIV-positive subjects.

BACKGROUND: The recently introduced IFN-γ release assay (IGRA) has been reported to improve the diagnosis of TB. However, IGRA has suboptimal sensitivity to diagnose TB among HIV co-infected subjects. Apart from IFN-γ, the pro inflammatory cytokines such as Interleukin-1beta (IL-1β), Tumor necrosis factor-alpha (TNF-α), IL-2, IL-6, IL-8 and IL-12 are also play a major role in mycobacterial infections. This study aimed to analyze these cytokines for detecting active TB among HIV sero positive subjects.

MATERIALS AND METHODS: We had prospectively enrolled 53 HIV positive subjects and 55 HIV-TB co-infected patients from India. IGRA was performed by using QuantiFERON TB-Gold In tube (QFT-GIT) method. TB antigen specific IL-1β, TNF-α, IL-2, IL-6, IL-8 and IL-12 levels were evaluated by ELISA in plasma harvested from QFT-GIT tubes.

RESULTS AND CONCLUSION: The TB antigen specific IL-1β levels were significantly elevated in HIV-TB co-infected patients compared to HIV positive subjects (p = 0.0004). The specificity of both IL-1β (50.94%) and QFT-GIT (52.83%) remained similar in HIV positive subjects (p = 0.24). However, IL-1β had shown higher sensitivity (72.73%) than QFT-GIT (54.55%) to diagnose TB among HIV co-infected patients. Moreover, in culture test positive HIV-TB patients, antigen specific IL-1β exhibited sensitivity of 84.21%; whereas QFT-GIT exhibited only 57.89% sensitivity. Unlike IFN-γ (the read out marker of QFT-GIT), antigen specific IL-1β levels were not influenced by low CD4 counts. The other cytokine levels were not significantly differ between the 2 groups.From this study we concluded that TB antigen specific IL-1β may be an additional biomarker for active TB diagnosis among HIV positive subjects.