Tuberculosis is a highly contagious disease caused by the microbial micobacterium tuberculosis. The source of infection is a sick person, animal, or carrier.
In adulthood, infection
with tubercle bacillus is almost 100%, however, with a sufficient level of immune defense, the development of the disease does not occur. Also, this good indicator is associated with timely
BCG vaccination, which is carried out for the first time in the first 3-7 days of the baby's life and is repeated in September of the first grade at school, and then at 14-15 years of age. However, it may happen that a child encounters a bacterial excretion even before revaccination, and a tuberculin test, known to everyone as Mantoux, is intended to detect this. It is carried out annually, regardless of the results of the previous reaction, the only contraindication to it is hypersensitivity to the administered drug. It is a hapten, i.e. defective antigen prepared from inactivated
mycobacterium tuberculosis. A tuberculin test is injected intradermally into the region of the middle third of the forearm, with a slight bloating, which is usually called the “button”.
Interpretation of the result
If the child has not yet been infected with mycobacteria, then the reaction will be negative, and this tubercle will not change in color and size. In this case, such a child will be revaccinated in adolescence. A positive tuberculin test is considered if, after 72 hours after administration of the drug, the infiltrate is equal to or more than 5 mm. At the same time, it can be hyperemic or remain unchanged in color. Also, the reaction to a tuberculin test can be doubtful or hyperergic, a more accurate assessment is carried out by a TB doctor. He also accepts children in whom the incidence of tuberculosis has been identified, such patients are subject to observation and treatment with special drugs. A tuberculin test is also used to select schoolchildren for BCG revaccination. Its assessment is necessary, first of all, to determine the degree of the immune activity of an organism and its protection against mycobacteria. The same is assessed with the introduction of the vaccine itself, that is, by the scar on the shoulder formed after BCG. In fact, the stronger the immunity of the child, the more pronounced the skin mark after it.
Method sensitivity
Since the tuberculin test is made intradermally, it is quite sensitive to external factors. However, contrary to the widespread myth that it cannot be wetted with water, it can still be done, it is only undesirable to use aggressive detergents, as well as rub the skin with a washcloth or comb it. All this can give a false positive result. More sensitive, including water, is the Pirke scarification test by applying a skin scratch, which, along with Mantoux, was carried out earlier for the diagnosis of tuberculosis. However, it is currently used much less frequently.