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 (Purified Protein Derivative) 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 such as taking medications that suppress the immune system.
Symptoms of an active TB infection include:
- Cough that lasts for three weeks or more
- Coughing up blood
- Chest pain
- Night sweats
- Unexplained weight loss
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 mucus 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 or Care Team.
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.
Source: MedlinePlus, National Library of Medicine