Immunological assays in the diagnosis of tuberculosis infection at the beginning of 21st century

A subject infected by tubercle bacilli may immediately develop the disease (primary tuberculosis), witch occurs in a few number of infected persons, or may overcome the primary infection (a latent carrier of the infection). Nowadays there are about two milliard people with a latent tubercular infection. About 10% of them will develop active tuberculosis during their lifetime. Detection of latent tuberculosis and its treatment decreases the risk of developing the active form of the disease. Until recently, the tuberculin test was a single screening method to identify the subjects with tubercular infection. In recent years, some novel in vitro tests to diagnose the tubercular infection have been designed. These tests measure the cell-mediated immune response quantifying the emission of interferon gamma by T cells in response to stimulation by Mycobacterium tuberculosis specific antigens. These tests are more sensitive and specific than the tuberculin skin test, but they are just an accessory tool, i.e., a link in the diagnostic chain of the tubercular infection.