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Health Services

Tuberculosis (TB)

EphNotes

The Meaning of a Positive PPD Skin Test

What is tuberculosis?

Tuberculosis, also called TB, is an infection caused by a bacteria. TB usually affects the lungs, but it can spread to the kidneys, bones, spine, brain, and other parts of the body.

What does it mean to have a positive PPD skin test?

The most commonly used skin test to check for TB is the PPD — purified protein derivative. If you have a positive PPD, it means you have been exposed to a person who has tuberculosis and you are now infected with the bacteria (mycobacterium tuberculosis) that causes the disease.

Do I have TB if I have a positive PPD test?

Not necessarily. A person can be infected with the bacteria that causes TB and NOT have the disease. Many people are infected with the bacteria, but only a few of these people (about 10%) go on to develop the disease. People who have the disease are said to have “active” TB.

People without active TB are called “latent.”

Healthy people who get infected with the tuberculosis bacteria are able to fight off the infection and do not get the disease. The bacteria is dormant in their lungs. If your body is not able to fight off the infection and the bacteria continues to grow, active TB develops.

Would I know if I developed active TB?

You might not know that you have active TB. Tuberculosis bacteria can grow in your body without making you feel sick. However, most people with active TB don’t feel well. People with TB often feel tired and have a cough that won’t go away. They may also lose weight or have a fever or break out in a sweat in bed. They may have trouble breathing.

Does a positive test mean that I can give TB to someone else?

Not necessarily. After you have a positive PPD skin test, you must have a chest x-ray and a physical exam to make sure that you don’t have active disease and that you are not contagious. If usually takes only a few days to tell whether you’re contagious. most people with a positive skin test ARE NOT contagious.

What will I have to do if my test is positive?

To be sure that you remain healthy, your health care practitioner may recommend that you take medication for 9 months to kill the tuberculosis infection. If you don’t take the medicine, the bacteria will remain in your lungs, and you will be in danger of getting active TB. The medicine to treat the TB infection is isoniazid, which is also called INH. You will need to take 1 pill every day for 9 months.

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