Tuberculosis | Diagnosis & Tests


How can my doctor check for tuberculosis?

The most commonly used method to check for tuberculosis is the PPD skin test. A PPD skin test is also called a Mantoux test. If you have a positive PPD, it means you have been exposed to a person who has tuberculosis and you have been infected with the bacteria that cause the disease.

If your PPD skin test is positive, you will likely have a chest X-ray and a physical exam to find out whether you have active TB and are currently contagious and able to spread the disease to other people.

It usually takes only a few days to tell whether you're contagious. Most people with a positive skin test are not contagious.

If I have a positive PPD test, do I have active tuberculosis?

Usually not. A person can be infected with the bacteria that cause tuberculosis but not actually have active tuberculosis. Of the people who are infected with the bacteria that cause tuberculosis, only a few (about 10%) go on to develop active TB.

Healthy people who get infected with the tuberculosis bacteria are often able to fight off the infection and do not develop active TB. The bacteria are dormant (inactive) in their lungs. If the body is not able to contain the infection and the bacteria continue to grow, active tuberculosis develops.

Would I know if I developed active tuberculosis?

There is a slight chance you might not know that you have developed active tuberculosis. Tuberculosis bacteria can grow in your body without making you feel sick. However, most people who have active tuberculosis experience symptoms.

If you develop active tuberculosis, you will need to be monitored medically (regular checkups and probably some chest X-rays) for the rest of your life to make sure you stay free of the tuberculosis disease, even after you have taken the full course of tuberculosis medicine.

Written by editorial staff

Reviewed/Updated: 04/14
Created: 11/96