tb skin test : Reading a TB Skin Test

What is latent TB infection?

For a TB skin test (also known as a PPD test), a healthcare worker will inject a small amount of fluid (called tuberculin or PPD) just under the skin on the underside of the forearm. After two or three days, you must return for the TB skin test reading.

You may have a swelling where the tuberculin was injected. The healthcare worker will measure this swelling and tell you if your reaction to the skin test is positive or negative. A positive reaction usually means that you have been infected by someone with Active Tuberculosis