What is the tuberculin skin test?
A TB skin test is used to help diagnose infection in children who have no symptoms. It contains a protein that is injected through a needle just under the skin. The area is then examined and measured between 48 to 72 hours later to see how big the bump on the skin is. A positive skin test implies that the child has tuberculosis infection or disease. It can take up to 3 months after becoming infected for the skin test to turn positive. Based on several factors, such as the presence of any symptoms, x-ray findings, underlying immune problems and travel to places where TB is common, the skin test is read as positive or negative. Routine tuberculosis skin testing of all children is not recommended. Rather, certain groups who are at risk for TB infection should be tested, which is why immigrants from countries with a high incidence of TB are always tested. The problem with testing everyone is that the test can be falsely positive in otherwise well children. What can happen if you come into
The tuberculin skin test tells if TB germs are in the body. A small amount of harmless fluid will be put just under the skin on your arm. Two or three days later you must return to the clinic to have your arm checked for a reaction. (The skin test must be repeated if you are not able to return to the clinic within 3 days.) If there is a reaction, the size of the reaction is measured.
