Tuberculosis and Testing

How to test at UHS:

Schedule an appointment by calling 734-764-8320 or see How to Get Health Care.

There are two types of tuberculosis (TB) testing. 

Skin testing can be used by most people. Skin testing is available at UHS weekdays except Thursday. You will need to return in person 48-72 hours after the test, so that your arm can be examined to evaluate the results of the test. Cost is $31. If you are a student, bring your U-M ID card with you. 

Skin testing is an easy, inexpensive skin test can indicate TB infection, either past or present. UHS uses the most reliable skin test, the Mantoux PPD. A small amount of fluid (called purified protein derivative or PPD) is injected under the top layer of skin on the lower arm with a small needle. You can do your normal activities after your skin test, including washing your arm. It may cause swelling, itching or tenderness at the site of injection, which usually disappears within a week. 

Blood testing may be preferred for individuals who received BCG vaccine, had a prior positive TB skin test, or had a documented allergic reaction to the TB skin test in the past. 

Frequently asked questions about testing:

What do test results mean?

  • negative (non-reactive) result means no evidence of TB, and no further testing is required.
  • A positive (reactive) result means there is evidence of TB, additional testing would be required, and you would need to meet with a clinician. 

If I’ve had a positive skin test in the past, should I have another test?
A blood test may be required after a positive skin test. The reaction to a skin test may be stronger if repeated frequently. It is important to keep your record of a positive skin test so you can refer to it in the future and not repeat skin tests. 

Especially for international patients:

Does vaccination cause a positive skin test?
The BCG TB vaccine generally does not cause a positive skin test result if you were vaccinated more than ten years ago. Many international patients received BCG vaccine, which reduced their TB risk as children. However, BCG vaccine effectiveness declines with time. Almost all international students who develop active TB have received the vaccine. TB infection, not BCG, causes most positive skin tests.

Will TB affect my visa status? 
TB test results do not affect visa status. UHS must report cases of active TB (but not inactive TB) to the county health department to be investigated for possible contagion of others. Beyond that, health records at UHS are confidential and cannot be released without your consent.

What is TB and how is it transmitted?

Tuberculosis is caused by TB bacteria. It usually affects the lungs. It can also affect other body parts such as the brain, kidneys or spine.

TB is spread from person to person through the air. The bacteria (in the form of droplets) are put into the air when a person with TB coughs or sneezes. People who are nearby inhale droplets and may become infected. TB is not as easily transmitted as colds.

What is the difference between inactive TB and active TB?

In inactive (latent) TB, TB bacteria are alive but inactive in the body. The body builds walls around these bacteria, the way a scab forms over a cut. TB bacteria can stay alive inside these walls for years. Up to 10% of people with inactive TB who do not receive treatment would develop active TB. 

In active TB (TB disease), TB bacteria become active and multiply. A person with active TB has symptoms and can spread TB to others. Active TB is very serious, causing permanent damage and even death.

For more information, see The Difference Between Latent TB Infection and TB Disease from the Centers for Disease Control and Prevention.

Who is at risk?

If you have lived in a country where TB is relatively common, you have a significant chance of having inactive TB. See list of High Burden Countries for tuberculosis. And uf you have inactive TB, your risk of developing TB disease in the US is highest during your first two years after arrival in the US. 

Other situations that may put you at risk are:

  • Close contact with a person who has active TB
  • Working or living in group facilities such as jails or prisons, nursing homes, hospitals, homeless shelters
  • Having health conditions including HIV infection, silicosis, diabetes mellitus, chronic renal failure, some blood disorders, some cancers, low body weight (>10% below ideal), gastrectomy and jejunoileal bypass, prolonged corticosteroid therapy, other immunosuppressive therapy
  • Injecting illicit drugs

TB has declined in the US, but it remains a threat to public health.

Testing for American travelers:

American travelers who anticipate prolonged stays (3 months or longer) in countries where tuberculosis is common should have TB skin testing pre-departure, and again 12 weeks after returning.See recommendations from the Centers for Disease Control and Prevention.


Inactive TB: In the US, treatment is recommended for those with inactive TB to prevent the development of active TB. In other countries where TB is more prevalent, treatment for inactive TB is not available or recommended because active TB is the greater priority.

Antibiotics are used to treat inactive TB in people.

Side effects of these antibiotics are uncommon, however they may affect the liver or nervous system. Liver inflammation (hepatitis) is the major concern. The risk is rare in young people and increases with age. Liver function can be monitored with blood tests. Side effects are usually reversed when the antibiotic is stopped. In the US, TB specialists believe that the risk of active TB is greater than the risk of side effects of treatment.

It is important to complete treatment, both to prevent active TB and to prevent development of strains that are resistant to antibiotics. If you are considering stopping treatment, please notify your clinician.

If you choose not to take treatment and later develop symptoms, inform a health care provider about the symptoms and positive TB test as soon as possible.

Active TB requires antibiotics, which can almost always cure active TB. Taking antibiotics as directed is critically important to success. Unfortunately antibiotic-resistant strains of TB are increasing. Active cases of TB are reported to the local health department, which would oversee treatment and may isolate the patient until antibiotics take effect. Your clinician would give you more information if active TB were diagnosed.


If you have inactive TB, get treated to protect your own health, plus your family, friends, co-workers and our community. Treatment eliminates TB bacteria from your body so it cannot develop into active TB. 

More information:

Washtenaw County Health Department  offers TB testing; call 734-544-6770

World Health Organization

Centers for Disease Control and Prevention