Tuberculosis is a highly contagious disease caused by the microbe micobacterium tuberculosis. The source of infection is a sick person, animal or carrier.
In adulthood, infection with a tubercle bacillus is almost 100%, but with a sufficient level of immune protection, the development of the disease does not occur. Also, this good indicator is associated with timely BCG vaccination, which is first carried out in the first 3-7 days of a baby’s life and is repeated in September of the first grade at school, and then at 14-15 years old. However, it may also happen that the child encounters a bacterioexcretor even before revaccination, and the 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 middlethird of the forearm, resulting in a slight swelling, which is usually called a "button".
Interpreting the result
If the child has not yet been infected with mycobacterium, 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, 72 hours after the 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 may be doubtful or hyperergic, a more accurate assessment is carried out by a phthisiatrician. He also accepts children who have been diagnosed with tuberculosis, 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 immune activity of the body and protection from mycobacteria. This is also assessed with the introduction of the vaccination itself, that is, by the scar on the shoulder that forms after BCG. In fact, the stronger the tension of the child's immunity, the more pronounced the skin mark after it will be.
Method sensitivity
Because the tuberculin test is performed intradermally, it is quite sensitive to external factors. However, contrary to the common myth that it cannot be wettedwater, it is still possible to do this, but it is undesirable to use aggressive detergents, as well as rub the skin with a washcloth or comb it. All this can lead to a false positive result. More sensitive, including to water, is the Pirquet scarification test by the method of applying a skin scratch, which, along with Mantoux, was previously carried out for the diagnosis of tuberculosis. However, it is now used much less frequently.
