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Tuberculosis Skin Testing


What is tuberculosis?

Tuberculosis (TB) is an infection caused by slow-growing bacteria. Tuberculosis usually causes lung disease but almost any part of the body can be affected.

TB infections are not common in the United States but can be a serious problem. At the time the infection is found, most infected children have no symptoms or X-ray signs of the disease. Most infections are discovered by a skin test before the infection has become serious enough to cause any problems.

If TB is found before symptoms develop, your child can be treated with medicines that will prevent the disease from progressing and spreading to others.

When should my child be tested?

Your child's healthcare provider will determine when and how often a skin test is needed. Most children in the U.S. do not need to be routinely tested.

Children at high risk for TB should have skin tests. A child is considered high risk if:

  • The child has been in close contact with people who have known or suspected TB infections.
  • The child has traveled to a country or has had a lot of contact with a person from a country where TB is common.

These children should have periodic TB skin tests:

  • Children with HIV or in contact with persons with HIV.
  • Children who were imprisoned.
  • Children in contact with homeless people, people who live in nursing homes, dormitories, or other facilities, or migrant farm workers.

TB can be a serious problem in children who have chronic conditions such as cancer, diabetes, kidney failure, malnutrition, or certain types of immune system problems. These children should be tested if there is a chance they have been exposed to TB.

How does the test work?

The Mantoux test is the most accurate skin test. For this test, your child's healthcare provider uses a shot to inject a small amount of protein from the tuberculosis bacteria into the top layer of your child's skin.

Your healthcare provider will want you to return to the office in 48 to 72 hours to check the area. If your child develops a red, raised, firm area around the test site, then your child was probably infected with TB at least 6 weeks earlier. The spot may not have a reaction if your child was infected less than 6 weeks ago.

Occasionally the redness will not appear for more than 72 hours after the test. Tell your child's provider if any redness appears. Your provider will decide if the redness is from a TB infection or from some other cause.

Although this test is more reliable than some other TB tests, sometimes it may give a false-positive or false-negative result.

Is there a vaccine for TB?

Bacillus Calmette-Guérin (BCG) is a vaccine given to help prevent tuberculosis. This vaccine is usually given to people who do not have TB but are likely to come in contact with people who have the disease. It is not routinely given in the U.S.

If your child has had the BCG vaccine, be sure to tell your child's healthcare provider. The BCG vaccine may cause the skin to turn red after a TB skin test, so that it looks like your child has TB even when he or she does not.

When should I call my child's healthcare provider?

Call your child's healthcare provider during office hours if:

  • Redness appears around the area where your child's skin was tested.
  • You believe your child may have been exposed to someone with tuberculosis.
  • You have other questions or concerns.

Written by Robert Brayden, MD, Professor of Pediatrics, University of Colorado School of Medicine.
Published by RelayHealth.
Last modified: 2010-11-09
Last reviewed: 2010-10-13

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a health care professional.

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