Dear Alice,

What does a positive result of a TB test mean? Once a person is positive, is that going to be positive for the rest of his/her life?

— Air-borne

Dear Air-borne,

You can be positive of one thing — you have asked an excellent question. People who test positive for tuberculosis (TB) have likely, at some point, been exposed to the TB-causing bacteria. In most cases, the body's immune system prevents the bacteria from causing sickness by building a wall around the bacteria. The bacteria may stay alive inside the body but are inactive. This is called TB infection or latent TB. People with TB infection don't have symptoms of TB and cannot spread the disease to others.

If the body's immune system is unable to stop the bacteria from growing, the bacteria can cause disease. People with TB disease or active TB usually have one or more symptoms of TB and may be contagious. Symptoms of TB affecting the lungs, the most common site of infection, include:

  • A cough lasting three or more weeks
  • Chest pain
  • Coughing up blood
  • Feeling weak or sick
  • Loss of appetite
  • Weight loss
  • Fever
  • Chills
  • Night sweats

Medicine is available to treat both TB infection (latent) and disease (active). Since people with TB infection can develop TB disease, a health care provider may prescribe antibiotics to kill off the inactive bacteria to prevent them from becoming active. For those with TB disease, a provider will probably prescribe several different antibiotics. These medications need to be taken as prescribed and finished — failing to do so can allow the bacteria to become drug-resistant, making the disease even more dangerous and difficult to cure.

Another reason a person might test positive is because they have received the TB vaccine. Many people from countries where TB is prevalent have had the vaccine, and may have a positive skin test. A chest x-ray can confirm they do not have active TB.

If you've tested positive for TB, see your health care provider to determine whether you have TB disease. Once you've had a positive TB result, your results will always be positive. You should not need to take the skin test again. Save the paper with your results; you may need it to show to a provider, employer, or school.

The good news is that with advances in medicine and public health, even active TB may no longer indicate imminent death ala Satine in Moulin Rouge!, but it is normal that testing positive may still cause one to feel concerned.


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