QuantiFERON TB2 Antigen Unit Converter

QuantiFERON TB2 Antigen (TB2 minus Nil) measures the amount of interferon-gamma (IFN-γ) released by your white blood cells in response to proteins specific to the tuberculosis (TB) bacterium. It is one component of the QuantiFERON-TB Gold Plus (QFT-Plus) blood test, which detects immune sensitization to Mycobacterium tuberculosis.

The TB2 tube contains short and long peptides from the TB-specific antigens ESAT-6 and CFP-10. These peptides stimulate both CD4+ helper T cells and CD8+ cytotoxic T cells. The reported value is the IFN-γ concentration in the TB2 tube after subtracting the background level measured in the Nil (negative control) tube.

A result of 0.35 IU/mL or higher is considered positive and suggests that the immune system has been exposed to TB bacteria. This test does not distinguish between latent TB infection and active TB disease.

The measured substance is interferon-gamma, a cytokine produced by T lymphocytes (white blood cells) circulating in the bloodstream. In this test, T cells that have been previously sensitized to Mycobacterium tuberculosis release IFN-γ when re-exposed to TB-specific peptide antigens in the laboratory tube.