Campus Health Services
Division of Student Affairs
The University of North Carolina at Chapel Hill

Information About The Tuberculin Skin Test (TST)

What is Tuberculosis (TB)?
Tuberculosis is an infection caused by the bacteria, Mycobacterium tuberculosis. With few exceptions TB is transmitted through droplets spread in the air from infected persons.  Most persons infected with M. tuberculosis have a latent (dormant) infection and do not develop TB disease and are not infectious. The likelihood that active TB disease will develop among adults with a good immune system who have latent M. tuberculosis infection (LTBI) is 5% to 15%. Among these persons, the risk for active disease development is greatest during the first two years after infection occurs. The risk declines markedly after this time period.  The greatest known risk factor that increases the likelihood that a person infected with M. tuberculosis will develop active disease is immunodeficiency, especially that caused by human immunodeficiency virus (HIV). Other immunocompromising conditions (e.g., diabetes mellitus, kidney failure, and treatment with immunosuppressive medications) also increase the risk for developing active TB disease, but to a lesser degree.

What is a Tuberculin Skin Test (TST)?
The tuberculin skin test (TST) is the standard method used to determine whether a person has been exposed to or is infected with Mycobacterium tuberculosis.  It is not an immunization that protects you from getting tuberculosis nor can it cause infection.

Who Should Receive a Tuberculin Skin Test?
The UNC-CH Health Care System uses a targeted screening program to identify those individuals most at risk for tuberculosis. The Center for Disease Control (CDC) of the United States has identified countries at low and high risk of endemic disease. This is just a reminder for all non-USA citizens and U.S. citizens living abroad in all countries except for those listed below who come to the University of North Carolina at Chapel Hill to provide the result of a skin test for tuberculosis (TST). Documentation of the TST is acceptable only from a U.S. facility trained in public health, occupational medicine, or an equivalent U.S. institution. Exceptions include: American Samoa, Austria, Australia, Belgium, British Virgin Islands, Canada, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Jamaica, Liechtenstein, Luxembourg, Malta, Monaco, Netherlands, New Zealand, Northern Ireland, Norway, San Marino, Scotland, St. Kitts and Nevis, St. Lucia, Sweden, Switzerland, United Kingdom and United States.

Who Should NOT Receive or Should DELAY Receiving a Tuberculin Skin Test?

• TST is contraindicated only for persons who have had a severe reaction (e.g., necrosis, blistering, anaphylactic shock, or ulcerations) to a previous TST.
• Individuals who have documented active TB or documented past treatment for TB should not have a TST.
• Individuals who have had a documented history of a positive result to a previous TST should not have a TST.
• Individuals who have had within the past 4-6 weeks certain viral infections (measles, influenza, mumps and probably others) or certain live vaccines (measles, mumps, rubella, varicella (chickenpox), oral typhoid, yellow fever, live-attenuated influenza (FluMist™), smallpox, oral polio) may have a false-negative result to a TST.  Note: TST can be placed the same day as the live vaccines or delay 4-6 weeks.
• Corticosteroids or immunosuppressive drugs within the past 4-6 weeks. (Note: The CDC states that prednisone (or equivalent) at >15mg/day for 2-4 weeks suppresses tuberculin reactivity.)

 
What Should I Do If I Have Previously Received a BCG (Bacille Calmette-Guerin) Vaccination?
If you have had a BCG vaccination, you still need to get a TST. The U.S. guidelines state that any positive TST result in a person (even those who have received BCG) should be treated as having a latent (dormant) TB infection.
 
Is Tuberculin Skin Testing Safe During Pregnancy?  Yes     Breastfeeding?     Yes

What Are Possible Side Effects of the Skin Test?
Infrequently, redness or other reactions may occur at the test site. In highly sensitized persons, strongly positive reactions to the tuberculin skin test may include blistering, ulceration, or necrosis at the test site. Cold packs or topical steroid preparations may be used for symptomatic relief of itching and discomfort. Scarring may result from strongly positive reactions.

What Must I Do after the Skin Test Is Placed on my Arm?
It is extremely important that you return within 48-72 hours to Campus Health Services to have the skin test read. If you do not return within 72 hours, the test will have to be repeated at your expense. A repeat TST can be administered again as soon as possible.

What Are Campus Health Services Hours for Administering and Reading Skin Tests?
8:15 AM - 4:00 PM, Monday through Friday. (TST’s are NOT placed on Thursdays.)

References:
1. Centers for Disease Control. Targeted Tuberculin Testing and Treatment of Latent Tuberculosis Infection. MMWR 2000;49(RR-6):1-43.
2. Tuberculin Skin Testing. TB Elimination. Centers for Disease Control. April 2006. http://www.cdc.gov/tb
3. Tuberculin Purified Protein Derivative (Mantoux)-Tubersol® product insert. Aventis Pasteur, Inc.;March 2002.                      
4. Centers for Disease Control. Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-care Settings, 2005. MMWR 2005;54(RR-17).
5. Targeted Tuberculin Testing and Interpreting Tuberculin Skin Test Results. TB Elimination. Centers for Disease Control. April 2005. http://www.cdc.gov/tb
6. Guide for Primary Health Care Providers: Targeted Tuberculin Testing and Treatment of Latent Tuberculosis Infection 2005. TB Elimination. Centers for Disease Control. Division of Tuberculosis Elimination. 2005. http://www.cdc.gov/tb
7. Shoreland, Inc. www.travax.com 2006.


Form No. PPD082006
CHS 7/2008  -  This article may be downloaded as a .pdf file from the "Documents and Forms" section, "Medical Services" area.