TB Testing

What is tuberculosis (TB)?

Tuberculosis (TB) is caused by germs that are spread through the air when a person with infectious TB coughs or sneezes. Anybody nearby is at risk of breathing these air-borne TB germs into their lungs.

When TB germs attack the lungs and grow, they cause damage to the lungs. People with TB germs growing in their lungs can spread TB germs to other people. TB can also affect other parts of the body like glands, bones, kidneys, and reproductive organs, although TB is not likely to be spread to others from tuberculosis in these parts of your body.

Infection or Disease?

You have TB infection when you have breathed TB germs into your lungs and your body’s defenses have stopped them from growing. You will not feel sick and you cannot spread TB germs to others. You have TB disease when the TB germs in your body start to grow and become active. When you have the disease, you may or may not feel sick, but it is really important to remember that you can spread TB germs to those around you.

Why do I need a tuberculin skin test?

You can have TB germs in your body and not feel sick. The skin test is the only way to tell if you have a TB infection.

How is the test done?

A tuberculin test is the first test given to check for TB. This is a two-part test.  In the first part, a small needle injects a small amount of a harmless test substance under the first layer of skin on your forearm. Although there is minimal risk, you will be asked to stay in the clinic for 15 minutes following the skin test to see if you experience any allergic reaction. The reaction you may get from this is a raised area where the needle was given. If this area gets itchy, do not scratch it. Instead apply cold (e.g., an ice cube) to this area.  The second part of the test is read two or three days later. You must go back to have your reaction to the injection measured.