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Tuberculosis and Testing

See also International Mandatory Tuberculosis Screening

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How to test at UHS: Tuberculosis (TB) skin testing is available weekdays except Thursday by appointment only. Same-day appointments may be available. Call 734-764-8325 for an appointment. If you are a student, bring your UM ID card with you.  You will need to return in person 48-72 hours after the test. Your arm will be examined to evaluate the results of the test. Cost is $10.

Frequently asked questions:

How is testing done?
An easy, inexpensive skin test can indicate TB infection, either past or present. University Health Service (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. After 48-72 hours, the test reaction must be measured, so you must return in person to have the test read.

What do results mean?
Possible results from a TB skin test are:

  • Negative (non-reactive) -- No further testing required.
  • Positive (reactive) -- A chest x-ray is required to check for active TB in the lungs. Possible chest x-ray results are:
    • Normal x-ray without symptoms indicates inactive TB. Treatment is recommended.
    • Normal x-ray with symptoms may require additional tests and/or treatment.
    • Abnormal x-ray may require additional tests and/or treatment.

What are side effects of the test?
The TB skin test will not make you sick. It may cause swelling, itching or tenderness at the site of injection, which usually disappears within a week.

If I’ve had a positive skin test in the past, should I have another test?
A new blood test may be appropriate, or it maybe necessary to repeat the skin test if no medical records are available and proof of TB status is required. The reaction may be stronger if repeated frequently, so it is important to keep your record of a positive skin test so you can refer to it in the future.

Can I do normal activities after the test?
Yes, you can do your normal activities, including washing your arm.

Does vaccination cause a positive skin test?
The vaccine (called BCG) generally does not cause a positive skin test if you were vaccinated more than ten years ago. TB infection causes most positive skin tests. Many international students 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.

Will TB affect my visa status?
TB test results do not affect your visa status. UHS must report cases of active TB (but not inactive TB) to county health departments 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 (TB) is a disease 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.

A person with inactive TB can develop active TB if they do not receive treatment (the lifetime risk is 1 in 10).

People with inactive TB:

  • Have no symptoms
  • Do not feel sick
  • Cannot spread TB to others
  • Have a positive (reactive) skin test
  • Can develop active TB

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

People with active TB may:

  • Have a bad cough longer than 3 weeks
  • Have pain in the chest
  • Cough up blood and sputum
  • Feel weak or tired
  • Lose appetite and weight
  • Have chills, fever or sweat at night

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. On average, TB is 20 times more common in Africa, Asia and Central and South America than in the US, Canada, Europe, Australia and New Zealand.

If you have inactive TB, your risk of developing TB disease in the US is highest during your first two years after arrival. About 35 per 100,000 international students have active TB when they arrive in the US. An additional 20-30 per 100,000 develop active TB each year of their stay.

More than 50% of cases of active TB in the US are in people born in countries with a higher prevalence of TB than 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

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. For additional information, see recommendations from the Centers for Disease Control and Prevention.

Treatment for 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.

An inexpensive antibiotic called isoniazid (INH) is recommended to eliminate TB germs. INH is recommended for people with:

  • Known recent infection (a positive skin test within two years of previous negative skin test)
  • Evidence of previous TB on chest x-ray
  • Other medical conditions that compromise the immune system, including:
    • Certain types of cancer
    • Diabetes
    • HIV infection
    • Rapid weight loss
    • Certain medications (e.g. cortisone treatment)

INH must be taken daily for nine months. To avoid side effects, you should also take vitamin B6 (10-50 mg) daily, eat a balanced diet, avoid Tylenol (acetaminophen) and avoid daily consumption of alcohol.

Side effects of INH are not common. However, INH 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 INH is stopped. In the United States, TB specialists believe that the risk of active TB is greater than the risk of side effects of INH.

For people who cannot take INH, alternative drugs are available.

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 INH and later develop symptoms, inform your clinician about the symptoms and positive TB skin test as soon as possible.

Treatment for active TB: Antibiotics can almost always cure active TB. However, antibiotic resistant strains of TB are increasing. Taking antibiotics as directed is critically important to success. Your clinician will give you more information if active TB is diagnosed.

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

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

Here's how you can prevent TB and other respiratory infections:

  • Cover your nose and mouth with a tissue every time you cough or sneeze. Throw the used tissue in a wastebasket. If you don’t have a tissue, sneeze or cough into your sleeve.
  • After coughing or sneezing, always clean your hands with soap and water or an alcohol-based hand cleaner.
  • Avoid touching your eyes, nose or mouth.
  • Do not share eating utensils, drinking glasses, towels or other personal items.
  • Stay home when you are sick.
  • If possible, avoid close contact with people who are sick.

Further information:

International Mandatory Tuberculosis Screening

UHS Allergy, Immunization and Travel Health Clinic
Offers TB testing -- call 734-764-8325 to schedule
Note: Language interpretation is available

UM International Center
734-764-9310

Washtenaw County Health Department
Offers TB testing
734-544-6770

World Health Organization

Centers for Disease Control and Prevention

Information in other languages from the Minnesota Department of Public Health