Anyone can get infected with TB, but some people are at higher risk. In the United States, getting tested for TB infection is not recommended for everyone. The recommendation to screen for TB infection is based on:
1) a person’s risk factors for having been exposed to TB germs
2) a person’s risk factors for progressing to active TB disease if infected with TB germs
The table below shows the high-level risk factors for TB infection and active TB disease:
| high risk factors for TB infection | high risk factors for developing active TB Disease |
|---|---|
Have had contact with a person with active infectious TB disease | Have recently been infected with TB (within the last 2 years) |
Were born in or frequently travel to countries where TB is common, including some countries in Asia, Africa, and Latin America | Have certain health conditions, examples include: |
Live or used to live in large group settings where TB is more common, such as homeless shelters, prisons, and jails | Take medicines or receive treatments that weaken the immune system, examples include: |
Work in places where TB is more likely to spread, such as hospitals, homeless shelters, correctional facilities, and nursing homes | Are under age 5 |
People living with HIV are more likely than people without HIV to become sick with active TB disease. This is because HIV weakens the immune system, making it harder for the body to fight germs. If you have HIV, talk to your health care provider about getting tested for TB.
If you think you should be screened for TB infection or you have been told you need to be screened for work or school, talk to your provider about getting tested. If you do not have a primary care provider, dial 2-1-1 to get connected with care.
If you are identified as a close contact of a person with active TB disease, the Health Department will help you get tested.
Check out this conversation guide from CDC that explains how to talk to your provider about LTBI.
There are two types of tests used to detect tuberculosis infection: the TB skin test (TST, PPD, tuberculin skin test) and the TB blood test (IGRA, QuantiFERON, T-Spot). A positive TB test result indicates that a person has been infected with TB. It cannot tell whether a person has a latent TB infection or active TB disease.
When someone has a positive TB test, other tests and assessments must be performed to make sure they do not have active TB disease. The next steps include a provider assessment, chest x-ray, and, if indicated, assessment of sputum (mucus deep in the chest) or other body fluid or tissue to look for the presence of TB germs. A person with symptoms of TB disease who has a negative TB test may still require further medical evaluation.
TB tests detect the presence of TB infection by measuring the body’s immune response to TB. The TB skin test and TB blood test will usually stay positive even after a person with LTBI or TB disease is treated. The TB skin test and TB blood test cannot be used to test for cure. People who know they have had a positive TB test in the past should keep a record of this result and share it with their healthcare providers.
Bacille Calmette-Guérin (BCG) is a vaccine for TB disease. This vaccine is not used in the United States, but many people born outside of the U.S. have had this vaccine. It is given to infants and small children in countries where TB is common. It can protect children from getting severe forms of TB disease, such as TB meningitis. The vaccine weakens over time and does not prevent TB infection. Many people in the United States diagnosed with TB disease have had the BCG vaccination in the past. People who have had the BCG vaccine can have a false positive TB skin test result when testing for TB infection. A false positive means the person had a positive TB test result but does not actually have TB infection. It is preferred that anyone who has had the BCG vaccine be tested using the TB blood test. There is no risk of a false positive related to past BCG vaccination when using the TB blood test to assess for TB infection.
People who have been exposed to active TB disease are recommended to be tested when the exposure is identified and then again 8-10 weeks after their last exposure to the infectious person. This is because it can take 8-10 weeks for the TB test to become positive after exposure. It is important to know that a person who is exposed to TB germs is not able to spread the germs to other people. Only people with active TB disease of the lungs or throat can spread TB germs to others.
As a part of TB prevention, the Health Department interviews people with active infectious TB to determine who they have had contact with while infectious. If a person is identified as one of these contacts, the Health Department will reach out to discuss the exposure and direct the person to testing. The Health Department can provide TB testing free of charge to people identified as close contacts to a person with active TB disease.
If you have been around someone with active TB, contact your health care provider to discuss your exposure. If you do not have a healthcare provider, contact your local health department.
Travelers who will be working in a health care setting where there are known TB patients should ask about procedures for preventing TB exposures.
Travelers who anticipate exposure to people with TB should have a TB skin or blood test before leaving the United States. If the test is negative, they should have a repeat test eight to 10 weeks after they return to the United States.
For additional information, consult with a travel clinic or with your health care professional about specific recommendations.
People with symptoms of TB disease or a positive blood or skin test for TB infection should be evaluated by a health care provider for TB disease. Latent TB Infection (LTBI) cannot be diagnosed until the clinician has taken steps to rule out the presence of TB disease. If a person is treated for LTBI when they have TB disease, it can result in inadequate treatment leading to treatment failure, drug resistance, and the ongoing spread of disease.
The medical evaluation for to rule out TB disease should include:
Medical history
Physical examination
Blood or skin test for TB infection
Chest x-ray
Other laboratory tests to see if TB germs are present, if clinically indicated
Laboratory tests for drug resistance, if a positive culture of TB disease is present
