To assess for exposure to or activation of certain diseases, most commonly tuberculosis (TB)

To assess the status of a child’s immune system during illness

To evaluate sensitivity to environmental antigens in the child with persistent symptoms

Make sure that the consent form is signed by the child’s parents or legal guardians.

Explain to the child and his parents that a small amount of antigenic material will be injected superficially or applied to the skin.

Inform the child and his parents that the testing takes only a few minutes for each antigen. Reactions will be evaluated 48 to 72 hours later.

The test may be repeated in 2 to 3 weeks if the first result is negative. The first test “reminds” the body that it was previously exposed to the antigen, and a response is noted on retesting. This is a common procedure for TB testing and is called the two-step test.

Ask the child and his parents about the child’s sensitivity to the test antigens, whether he has had previous skin testing, and what the outcomes of that testing were.

Ask the child and his parents if the child has had TB or been exposed to it and if he has had the bacilli Calmette-Guerin vaccination.