If your PPD test is positive, it signifies that you have been exposed to a person who has tuberculosis and you are now infected with the bacteria (mycobacterium tuberculosis) that causes the disease. This is the primary indication of a positive purified protein derivative (PPD) skin test.
The PPD test is the most commonly used skin test to check for tuberculosis (TB). It involves injecting a small amount of purified protein derivative under the skin, usually on the forearm. After 48 to 72 hours, a healthcare professional examines the injection site for a reaction.
Understanding a Positive PPD Result
A positive PPD result is a significant indicator that your body has mounted an immune response to the Mycobacterium tuberculosis bacteria. This immune response suggests an infection has occurred.
Here's what a positive PPD result implies:
- Exposure to Tuberculosis: It means you have come into contact with someone who has active tuberculosis. This exposure led to the bacteria entering your system.
- Bacterial Infection: You are now infected with the bacteria (mycobacterium tuberculosis) that causes TB. This does not necessarily mean you have active, symptomatic TB disease, but rather that the bacteria are present in your body.
- Immune Response: Your immune system has recognized the bacteria and created antibodies or T-cells to fight it off, which is what causes the reaction on the skin during the test.
What Does "Infected" Mean?
Being "infected with the bacteria" means the Mycobacterium tuberculosis has entered your body and is present, but it doesn't automatically mean you have active, contagious TB disease. People who are infected but do not have active disease are often referred to as having latent TB infection. In this state:
- The bacteria are present in your body but are inactive.
- You typically do not experience symptoms of TB disease.
- You cannot spread the bacteria to others.
However, latent TB infection can progress to active TB disease in the future, especially if your immune system weakens. Therefore, a positive PPD test typically prompts further evaluation by a healthcare professional to determine if the infection is latent or active, and to discuss appropriate next steps, which may include treatment to prevent the development of active disease.
