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Skin Testing
| A TB skin test is the only way to find out
if you have latent TB infection. You can get a skin test at the health
department or at your doctor's office. You should get tested for TB if: |
- you have spent time with a person with known or suspected to have TB disease
- you have HIV infection or another condition that puts you at high risk for TB disease
- you think you might have TB disease
- you are from a country where TB disease is very common (most countries in Latin America
and the Caribbean, Africa, Asia, Eastern Europe, and Russia)
- you inject drugs
- you live somewhere in the U.S. where TB disease is more common (homeless shelters,
migrant farm camps, prisons and jails, and some nursing homes)
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A health care worker can give you the TB skin test. The health care worker will inject a small
amount of testing fluid (called tuberculin) just under the skin on the lower part of
your arm. After 2 or 3 days, the health care worker will measure your reaction to the
test. You may have a small bump where the tuberculin was injected. The health care
worker will measure this bump and tell you if your reaction to the test is positive or
negative. A positive reaction usually means that you have latent TB infection.
If you have a positive reaction to the skin test, your doctor or nurse may do other tests
to see if you have TB disease. These tests usually include a chest x-ray and a test of the
sputum you cough up.
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Because the TB bacteria may be found somewhere besides your lungs,
your doctor or nurse may check your blood or urine, or do other tests. If you have TB
disease, you will need to take medicine to cure the disease. If you have TB infection,
and TB disease has been ruled out, your doctor or nurse may offer you treatment to prevent
the future development of TB disease.
Additional testing is necessary if you have recently spent time with someone with infectious
TB due to the fact that your skin test reaction may not be positive yet. You may need
a second skin test 10 to 12 weeks after the last time you spent time with the infectious
person. This is because it can take several weeks after infection for your immune
system to be able to react to the TB skin test. If your reaction to the second test
is negative, you probably do not have latent TB infection.
| If you were vaccinated with (Bacillus of Calmette and Guérin) BCG, you may have a positive
reaction to a TB skin test. This reaction may be due to the BCG vaccine itself or
to latent TB infection. But your positive reaction probably means that you have latent TB infection if: |
- you recently spent time with a person who has TB disease
- you are from an area of the world where TB disease is very common (most countries in
Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia)
- you spend time where TB is common (homeless shelters, drug-treatment centers,
health care clinics, jails, prisons)
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