[Tuberculin intradermal reaction (IDR) or tuberculin test].

Tuberculinic switch is defined as an increase of the intradermal reaction diameter in two tests carried out within three months of each other. The tuberculinic skin reaction proves the presence of a delayed hypersensitivity induced by mycobacterial antigens (Mycobacterium tuberculosis, BCG, some atypical mycobacteria). However, this reaction does not always prove an effective protection against the BK. The intradermal injection of a purified Purified Protein Derivative (PPD) resulting from a culture of M. tuberculosis is the only method validated for the diagnosis of tuberculosis infection (latent infection) and screening for hypersensitivity and post-vaccine BCG (Official French decree No 96-775 of September 5, 1996 and its decree relating to vaccination by BCG and tuberculin tests). The guidelines concerning tuberculin testing are: investigating on a case of tuberculosis; tracking or surveillance of people frequently exposed to tuberculosis (examination on recruitment and follow-up of exposed professionals); prevaccine testing in children over four weeks of age.