RESUMEN
Infection with Mycobacterium tuberculosis causes primarily formation of granulomatous tubercles in the lungs. In the absence of any clinical symptoms it is named latent tuberculosis infection which can be an origin of reactivation, especially as a consequence of an impaired response of the immune system. Complete anamnesis, radiographic methods and bacteriological analysis (microscopy, culture, PCR) are useful for diagnosis of tuberculosis. Since 2005 newer in vitro tests are available using interferon-gamma release assays (IGRAs). Compared to the tuberculin skin test it is possible to differentiate between infection with M. tuberculosis and individuals vaccinated with the Bacillus Calmette-Guérin (BCG) vaccine. These new in vitro tests are part of a screening procedure which has to be performed before starting immunosuppressive therapy with tumor necrosis factor-alpha (TNF-α) inhibitors. In cases of latent tuberculosis infection administration of isoniazid for 9 months is recommended.