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a sterile liquid containing the growth products of, or specific substances extracted from, the tubercle bacillus; used in various forms in the diagnosis of tuberculosis (see tuberculin test).
Old tuberculin a sterile solution of a heat-concentrated filtrate of tubercle bacillus culture grown on a special medium, used for tuberculin tests.
PPD tuberculin (purified protein derivative tuberculin) a sterile solution of a purified protein fraction precipitated from a filtrate of tubercle bacillus culture grown on a special medium, used for tuberculin tests.
tuberculin test any of a large number of skin tests for tuberculosis using a variety of different types of tuberculin and methods of application. The most reliable procedure, now standard, is intradermal injection (the mantoux test) of PPD (purified protein derivative); a positive result consists of a palpable and visible area of erythema and induration greater than 10 mm in diameter developing around the site of injection 48 to 72 hours after the injection. Intermediate strength tuberculin (5 TU) is generally used to test adults; a positive result is virtually diagnostic of a previous or current infection with Mycobacterium tuberculosis. Persons with a negative test are retested with second strength tuberculin (250 TU); in this test a positive reaction is frequently due to atypical mycobacteria infection and is thus nonspecific; a negative result indicates either absence of tuberculosis or the presence of cutaneous anergy due to overwhelming tuberculosis infection or to an associated immunocompromised condition such as HIV infection, Hodgkin's disease, or sarcoidosis.
Etymology: ME, ald + L, tubercle
the original formula for an extract of the tubercle bacillus used in the treatment of tuberculosis by Koch, using a glycerin-broth culture of Mycobacterium tuberculosis after filtration and concentration of the liquid.