Do I need a test for latent tuberculosis?

What the USPSTF recommends

Increased risk includes people born in, or former residents of, countries with high tuberculosis rates, and people who live or have lived in high-risk group settings such as homeless shelters or correctional facilities (USPSTF 2023). Local patterns vary, so clinicians can ask their local or state health department about other groups at risk in their area (USPSTF 2023). The benefit depends on follow-up: people who screen positive need further checks and treatment (USPSTF 2023).

According to the CDC, tuberculosis is common in most countries in Latin America, the Caribbean, Africa, Asia, Eastern Europe and Russia, as cited by the USPSTF (USPSTF 2023). In 2020, 71.5% of active tuberculosis cases in the US were in people born outside the US (USPSTF 2023).

Latent vs active tuberculosis

In latent tuberculosis the bacteria are alive but held in check by the immune system. People with it have no symptoms, do not feel sick and cannot spread it, but it can turn into active disease without treatment (USPSTF 2023). An estimated 5% of people in the US, or up to 13 million, have latent infection. About 30% of people exposed become infected, and without treatment about 5% to 10% of healthy people go on to active disease (USPSTF 2023). Active tuberculosis usually affects the lungs, can spread to others, and can cause weakness, weight loss, fever, loss of appetite, chills, night sweats, a bad cough, chest pain or coughing up blood (USPSTF 2023).

Skin test or blood test

Two screening tests are used in the US. The tuberculin skin test (TST) is placed under the skin and must be read by trained staff 48 to 72 hours later, so you return for a second visit. The interferon-gamma release assay (IGRA) is a single blood draw (USPSTF 2023). The blood test may be the better choice for people who had the BCG vaccine, because it does not react to the vaccine, and for people who may not be able to come back to have a skin test read (USPSTF 2023). A positive result is followed by a medical history, an exam, a chest X-ray and other tests to rule out active disease (USPSTF 2023).

How often to test

There is no evidence on the best interval. The USPSTF suggests basing it on risk: from a single test for people unlikely to be exposed again, to a yearly test for people with ongoing exposure (USPSTF 2023).

Treatment

Several antibiotics treat latent tuberculosis. Shorter courses, often combining isoniazid with rifapentine or rifampin, are now preferred over long isoniazid-only courses, partly because of liver side effects; the CDC keeps the current treatment advice (USPSTF 2023). No studies directly reported harms of screening; possible harms include stigma and treatment after a false-positive result (USPSTF 2023).

Common questions

I have diabetes. Should I be screened?

Poorly controlled diabetes has been linked to latent infection turning active, but the evidence was too limited for a separate USPSTF recommendation (USPSTF 2023). Ask your clinician.

I need a TB test for work. Is that this?

Testing of health care workers and staff in shelters or prisons is done through employee health programs, so the USPSTF did not review it (USPSTF 2023). Follow your employer's rules.

Also see the HIV screening check, the hepatitis B screening check, the lung cancer screening check and all screening tests by age.