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Latent
TB Infection
How can you get tested for TB? 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:
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 phlegm you cough up. 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 recently spent time with someone with infectious TB, 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.  What if you have been vaccinated with BCG? BCG is a vaccine for TB. This vaccine is often given to infants and small children where TB is common. BCG vaccine does not always protect people from TB. If you were vaccinated with 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:
If you have TB infection, how can you keep from developing TB disease? Many people who have latent TB infection never develop TB disease. But some people who have latent TB infection are more likely to develop TB disease than others. These people are at high risk for TB disease. They include:
If you have latent TB infection (a positive skin test
reaction) and you are in one of these high-risk groups, you need to take
medicine to keep from developing TB disease. This is called treatment
for latent TB infection. There are many treatment options. You and your
health care provider must decide which treatment is best for you. The medicine usually used for the treatment of latent TB infection is a drug called isoniazid or INH. INH kills the TB bacteria that are in the body. If you take your medicine as prescribed, treatment for latent TB infection will keep you from ever developing TB disease. Most people must take INH for at least 6 to 9 months. Children and people with HIV infection may need to take INH for a longer time. Sometimes people are given treatment for latent TB infection even if their skin test reaction is not positive. This is often done with infants, children, and HIV-infected people who have recently spent time with someone with infectious TB disease. This is because they are at very high risk of developing serious TB disease soon after they become infected with TB bacteria. It is important that you take all the pills prescribed for you so that your treatment for latent TB infection is effective. If you start taking INH, you will need to see your doctor or nurse on a regular schedule. He or she will check on how you are doing. Very few people have serious side effects to INH. However, if you have any of the following side effects call your doctor or nurse right away:
Warning: Drinking alcoholic beverages (wine,
beer, and liquor) while taking INH can be dangerous. People who have latent TB infection but do not receive treatment for latent TB infection need to know the symptoms of TB. What
if you have HIV infection? A person can have latent TB infection for years without any signs of disease. But if that person's immune system gets weak, the infection can quickly turn into TB disease. Also, if a person who has a weak immune system spends time with someone with infectious TB, he or she may become infected with TB bacteria and quickly develop TB disease. Because HIV infection weakens the immune system, people with latent TB infection and HIV infection are at very high risk of developing TB disease. All HIV-infected people should be given a TB skin test to find out if they have latent TB infection. If they have latent TB infection, they need treatment for latent TB infection as soon as possible to prevent them from developing TB disease. If they have TB disease, they must take medicine to cure the disease. TB disease can be prevented and cured, even in people with HIV infection. |
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