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What Is a PPD Test and Why Do I Need One?

Tuberculosis, or TB, is one of the world’s leading infectious disease killers – and the bacteria that cause tuberculosis can live in your body for years without symptoms. In the United States, the Centers for Disease Control and Prevention (CDC) estimates that up to 13 million people live with inactive tuberculosis.

Inactive tuberculosis can become active at any time, striking your lungs, kidneys, spine, brain, or any other part of your body. Tuberculosis can be contagious, and Pennsylvania schools, healthcare facilities, and other workplaces require tuberculosis testing.

While blood tests are becoming more popular, the most commonly used test for tuberculosis is a PPD skin test. Keep reading to find out how it works and why it’s important to get one!

How do PPD tests work?

The process for a PPD test is quite simple. Your vybe clinician will inject 0.1 ml of tuberculin purified protein derivative (or PPD) under the top layer of skin on your arm. A bump or small welt will form, which usually goes away in a few hours. Return to vybe within 48-72 hours, and we’ll check the injection site for your reaction to the PPD. That’s it!

(Note: if you do not return within 72 hours, you will need to retake the test.)

Does a PPD test hurt?

No, although you might feel a slight pinch or sting during the injection. There’s a very small risk of severe redness and swelling on your arm, especially if you’ve had a positive PPD test in the past and are testing in the same area again.

How often do you need a PPD test?

We recommend getting a TB test every three years unless you’ve had potential exposure or are involved in high-risk activity—in which case getting retested should be sooner. Ask your vybe clinician for further guidance.

Healthcare workers, correctional facility employees, and those that work with the homeless should get tested multiple times throughout the year.

What does a negative PPD test mean?

A negative result usually means that you have not been infected with the bacteria that cause tuberculosis.

What does a negative PPD test look like?

After 48-72 hours, the area where you received the PPD injection is not swollen or only slightly swollen. However, the CDC confirms the measurements are different for high-risk groups.

For example, someone who is immuno-suppressed, has HIV, or recently came into contact with an infected person cannot have swelling greater than 5 mm. Infants and children or people who live or work in places where tuberculosis infection is more likely cannot exceed 10 mm.

What does a positive PPD test mean?

 A positive result usually means that you are infected with tuberculosis bacteria. Your vybe clinician will do additional testing to find out if you have inactive or active tuberculosis.

What does a positive PPD test look like?

In people with no known risk of tuberculosis, 15 mm or more of swelling at the injection site indicates a positive test.

Who should get a PPD test vs. a blood test?

You may prefer a blood test if you don’t want to come back in 48-72 hours to assess your reaction to the PPD injection. People who have already received a tuberculosis vaccine should also opt for a blood test.

All vybe urgent care centers offer a skin test (PPD test) and a blood test that can detect inactive tuberculosis in the body:

  • Mantoux tuberculin skin test
  • QuantiFERON®-TB Gold Plus (QFT-Plus) blood test

Where can I get a PPD test?

All vybe urgent care centers offer PPD testing. We’re open seven days a week with extended weekday evening hours, making it easy to get your tuberculosis test of choice done quickly.