QuantiFERON-TB Gold Plus TB1 Antigen Unit Converter

The QuantiFERON-TB Gold Plus TB1 Antigen (QFT-Plus TB1) is one component of a blood test used to detect Mycobacterium tuberculosis infection. It measures how much interferon-gamma (IFN-γ) your immune cells release when exposed to TB-specific proteins.

The QFT-Plus test uses four blood collection tubes. The TB1 tube contains peptides from two proteins, ESAT-6 and CFP-10, that are found in the TB bacterium but absent from BCG vaccine strains and most other mycobacteria. These peptides are designed to stimulate CD4+ T-helper cells that have previously encountered TB.

The TB1 result is always interpreted alongside the Nil tube (background control) and Mitogen tube (positive control). A TB1 value on its own cannot determine TB status. The Nil value is subtracted from TB1 to calculate the TB-specific response, and the Mitogen tube confirms that your immune cells are functioning properly.

The IFN-γ measured in the TB1 tube is produced by CD4+ T-helper lymphocytes circulating in the blood. These T cells release IFN-γ when they recognize the TB-specific ESAT-6 and CFP-10 peptides, which only occurs if the immune system has previously been exposed to Mycobacterium tuberculosis.