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Tuberculosis Screening

What is a tuberculosis (TB) screening?

This test checks to see if you have been infected with tuberculosis, commonly known as TB. TB is a serious bacterial infection that mainly affects the lungs. It can also affect other parts of the body, including the brain, spine, and kidneys. TB is spread from person to person through coughing or sneezing.

Not everyone infected with TB gets sick. Some people have an inactive form of the infection called latent TB. When you have latent TB, you don't feel sick and can't spread the disease to others.

Many people with latent TB will never feel any symptoms of the disease. But for others, especially those who have or develop weakened immune systems, latent TB can turn into a far more dangerous infection called active TB. If you have active TB, you may feel very sick. You may also spread the disease to other people. Without treatment, active TB can cause serious illness or even death.

There are two types of TB tests used for screening: a TB skin test and a TB blood test. These tests can show if you have ever been infected with TB. They don't show if you have a latent or active TB infection. More tests will be needed to confirm or rule out a diagnosis.

Other names: TB test, TB skin test, PPD test, IGRA test

What is it used for?

TB screening is used to look for a TB infection in a skin or blood sample. The screening can show whether you have been infected with TB. It does not show if TB is latent or active.

Why do I need a TB screening?

You may need a TB skin test or TB blood test if you have symptoms of an active TB infection or if you have certain factors that put you at higher risk for getting TB.

Symptoms of an active TB infection include:

In addition, some childcare centers and other facilities require TB testing for employment.

You may be at higher risk for getting TB if you:

  • Are a health care worker who cares for patients who have or are at high risk for getting TB
  • Live or work in a place with a high rate of TB infection. These include homeless shelters, nursing homes, and prisons.
  • Have been exposed to someone who has an active TB infection
  • Have HIV or another disease that weakens your immune system
  • Use illegal drugs
  • Have traveled or lived in an area where TB is more common. These include countries in Asia, Africa, Eastern Europe, Latin America, and the Caribbean, and in Russia.

What happens during a TB screening?

A TB screening will either be a TB skin test or a TB blood test. TB skin tests are used more often, but blood tests for TB are becoming more common. Your health care provider will recommend which type of TB test is best for you.

For a TB skin test (also called a PPD test), you will need two visits to your health care provider's office. On the first visit, your provider will:

  • Wipe your inner arm with an antiseptic solution
  • Use a tiny needle to inject a small amount of PPD under the first layer of skin. PPD is a protein that comes from the tuberculosis bacteria. It is not live bacteria, and it will not make you sick.
  • A small bump will form on your forearm. It should go away in a few hours.

Be sure to leave the site uncovered and undisturbed.

After 48-72 hours, you will return to your provider's office. During this visit, your provider will check the injection site for a reaction that may indicate a TB infection. This includes swelling, redness, and an increase in size.

For a TB test in blood (also called an IGRA test), a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't any special preparations for TB skin test or a TB blood test.

Are there any risks to the test?

There is very little risk to having a TB skin test or blood test. For a TB skin test, you may feel a pinch when you get the injection.

For a blood test, you may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If your TB skin test or blood test shows a possible TB infection, your health care provider will probably order more tests to help make a diagnosis. You may also need further testing if your results were negative, but you have symptoms of TB and/or have certain risk factors for TB. Tests that diagnose TB include chest x-rays and tests on a sputum sample. Sputum is a thick mucous coughed up from the lungs. It is different than spit or saliva.

If not treated, TB can be deadly. But most cases of TB can be cured if you take antibiotics as directed by your health care provider. Both active and latent TB should be treated, because latent TB can turn into active TB and become dangerous.

If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about a TB screening?

Treating TB takes much longer than treating other types of bacterial infections. After a few weeks on antibiotics, you will no longer be contagious, but you will still have TB. To cure TB, you need to take antibiotics for at least six to nine months. The length of time depends on your overall health, age, and other factors. It's important to take the antibiotics for as long as your provider tells you, even if you feel better. Stopping early can cause the infection to come back.

References

  1. American Lung Association [Internet]. Chicago: American Lung Association; c2018. Diagnosing and Treating Tuberculosis [updated 2018 Apr 2; cited 2018 Oct 12]; [about 4 screens]. Available from: https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/tuberculosis/diagnosing-and-treating-tuberculosis.html
  2. American Lung Association [Internet]. Chicago: American Lung Association; c2018. Tuberculosis (TB) [cited 2018 Oct 12]; [about 3 screens]. Available from: https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/tuberculosis
  3. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Fact Sheets: Tuberculosis: General Information [updated 2011 Oct 28; cited 2018 Oct 12]; [about 4 screens]. Available from: https://www.cdc.gov/tb/publications/factsheets/general/tb.htm
  4. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Tuberculosis Facts: Testing for TB [updated 2016 May 11; cited 2018 Oct 12]; [about 3 screens]. Available from: https://www.cdc.gov/tb/publications/factseries/skintest_eng.htm
  5. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Tuberculosis: Signs and Symptoms [updated 2016 Mar 17; cited 2018 Oct 12]; [about 3 screens]. Available from: https://www.cdc.gov/tb/topic/basics/signsandsymptoms.htm
  6. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Tuberculosis: Who Should be Tested [updated 2016 Sep 8; cited 2018 Oct 12]; [about 3 screens]. Available from: https://www.cdc.gov/tb/topic/testing/whobetested.htm
  7. Lab Tests Online [Internet]. Washington D.C: American Association for Clinical Chemistry; c2001–2018. IGRA TB Test [updated 2018 Sep 13; cited 2018 Oct 12]; [about 2 screens]. Available from: https://labtestsonline.org/tests/igra-tb-test
  8. Lab Tests Online [Internet]. Washington D.C: American Association for Clinical Chemistry; c2001–2018. Sputum [updated 2017 Jul 10; cited 2018 Oct 12]; [about 2 screens]. Available from: https://labtestsonline.org/glossary/sputum
  9. Lab Tests Online [Internet]. Washington D.C: American Association for Clinical Chemistry; c2001–2018. TB Skin Test [updated 2018 Sep 13; cited 2018 Oct 12]; [about 2 screens]. Available from: https://labtestsonline.org/tests/tb-skin-test
  10. Lab Tests Online [Internet]. Washington D.C: American Association for Clinical Chemistry; c2001–2018. Tuberculosis [updated 2018 Sep 14; cited 2018 Oct 12]; [about 2 screens]. Available from: https://labtestsonline.org/conditions/tuberculosis
  11. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2018. Tuberculosis: Diagnosis and treatment; 2018 Jan 4 [cited 2018 Oct 12]; [about 4 screens]. Available from: https://www.mayoclinic.org/diseases-conditions/tuberculosis/diagnosis-treatment/drc-20351256
  12. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2018. Tuberculosis: Symptoms and causes; 2018 Jan 4 [cited 2018 Oct 12]; [about 3 screens]. Available from: https://www.mayoclinic.org/diseases-conditions/tuberculosis/symptoms-causes/syc-20351250
  13. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2018. Tuberculosis (TB) [cited 2018 Oct 12]; [about 2 screens]. Available from: https://www.merckmanuals.com/home/infections/tuberculosis-and-related-infections/tuberculosis-tb
  14. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests [cited 2018 Oct 12]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
  15. UF Health: University of Florida Health [Internet]. Gainesville (FL): University of Florida; c2018. PPD skin test: Overview [updated 2018 Oct 12; cited 2018 Oct 12]; [about 2 screens]. Available from: https://ufhealth.org/ppd-skin-test
  16. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2018. Health Encyclopedia: TB Screening (Skin) [cited 2018 Oct 12]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=tb_screen_skin
  17. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2018. Health Encyclopedia: TB Screening (Whole Blood) [cited 2018 Oct 12]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=tb_screen_blood

The medical information provided is for informational purposes only, and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.

In the event of a medical emergency, call 911 immediately.