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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.

Tuberculosis infections continue to be a serious problem for children. At the time the infection is discovered, 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 detected before symptoms develop, your child can be treated with medications that will prevent the disease from continuing and spreading to others.

When should my child be tested?

Your child's health care 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 with a high incidence of TB or has had a lot of contact with a person from another country where TB is common.

Children with the following should have periodic TB skin tests:

  • Children with HIV or in contact with persons with HIV.
  • Children that were imprisoned.
  • Children in contact with homeless persons, nursing home residents, institutionalized or imprisoned persons, 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 health care 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 health care 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 tuberculosis bacteria 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 doctor if any redness appears. Your doctor will decide if the redness is from a tuberculosis 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-Guerin (BCG) is a vaccination given to 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 a routine vaccination in the U.S.

If your child has had the BCG vaccine, be sure to tell your child's doctor. The BCG vaccine may cause the skin to become red after a TB skin test, suggesting that your child has TB even when he or she does not.

When should I call my child's doctor?

Call your child's doctor 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, Associate Professor of Pediatrics, University of Colorado School of Medicine.
Published by McKesson Provider Technologies.
Last modified: 2003-08-12
Last reviewed: 2006-08-22
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 healthcare professional.
Copyright 2006 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.
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