Performance Evaluation of the VIDAS TB-IGRA Assay.

Tuberculosis (TB) infection is one of the top 10 causes of death in the world and the leading cause of death due to a single infectious agent. Millions of people are infected with TB each year which can pose significant economic and health care burdens on the global population. TB can infected the lungs (pulmonary TB) or other organs such as the brain, and kidneys (extra-pulmonary TB). When a person with pulmonary TB coughs or sneezes, water droplets containing M. tuberculosis are expelled into the air. Persons can become infected with TB when they inhale air containing these water droplets, however, not everyone infected with Mycobacterium tuberculosis (Mtb) becomes ill. Therefore two TB-related conditions exist: latent TB infection (LTBI) and TB disease. People with latent TB infection are not ill and do not present TB symptoms or have TB disease. The only sign of TB infection is a positive reaction to the tuberculin skin test or TB blood tests such as IGRA tests. People with latent TB infection are not contagious and cannot spread TB infection to others. Identification and treatment of LTBI can substantially reduce the risk of developing active disease. However, there is no diagnostic gold standard for LTBI. Two types of test are currently available for the identification of LTBI: the tuberculin skin test (TST) and the TB Interferon Gamma (IFN-γ) Release Assay (TB-IGRA). Evidence suggests that both TST and TB-IGRA are acceptable but not perfect because they detect indirect markers of Mtb exposure and indicate a cellular immune response to M. tuberculosis. TB-IGRAs have a number of advantages compared to TST which promote their progressive adoption in the clinical practice and in guidelines.