Tuberculosis & PPD Testing
New job? Risk of exposure?
Tuberculosis testing is vital.
Tuberculosis (TB) is a severe respiratory disease caused by bacteria that are spread through the air from person to person. While the bacteria usually attack the lungs, they can also attack any part of the body such as the kidney, spine, and brain. If left untreated, tuberculosis can be fatal.
What are common TB symptoms?
Per the Centers for Disease Control and Prevention, symptoms of tuberculosis include:
- Unexplained weight loss and loss of appetite
- Night sweats
- Coughing for three weeks
- Hemoptysis (coughing up blood)
- Chest pain
What are common causes?
Tuberculosis is spread through the air from one person to another. People nearby may breathe in these bacteria and become infected. However, not everyone who inhales TB bacteria will get sick.
In most cases, people who breathe in TB bacteria and become infected are able to naturally fight the bacteria to stop them from growing. The bacteria then becomes inactive, but remains in the body and can become active later. This is called latent TB infection. While cases of tuberculosis in the US have been greatly reduced, it is still a life-threatening illness affecting thousands of people.
Testing & treatment options
There are two kinds of tests that are used to detect TB bacteria in the body: the TB skin test (TST) and TB blood tests. A positive TB skin test or TB blood test only tells you if you’ve been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease.
First off, the TB skin test has many names that can be confusing because they’re used interchangeably: Mantoux tuberculin skin test, TB skin test, tuberculin skin test (TST), and PPD.
How are these names related?
Mantoux refers to the technique for administering the test. Tuberculin (also called purified protein derivative or PPD) is the solution injected to determine the test result.
Whatever name you use for the TB skin test, the test requires two visits with a health care provider. On the first visit the health care worker places the test; on the second visit the health care provider reads the test.
- The TB skin test requires injecting a small amount of fluid (called tuberculin, also called pure protein derivative or PPD) into the skin on the lower part of your arm.
- After you receive the tuberculin skin test you must return within 48 to 72 hours to have a trained health care worker look for a reaction on the arm.
- The result depends on the size of the raised, hard area or swelling.
- If the test indicates that you’re infected with TB bacteria, you’ll receive other tests to see if you have latent TB infection or TB disease.
TB blood tests are also called interferon-gamma release assays or IGRAs. Two TB blood tests are approved by the U.S. Food and Drug Administration (FDA) and are available in the U.S.: the QuantiFERON®-TB Gold Plus (QFT-Plus) and the T-SPOT®.TB test (T-Spot). A health care provider will draw your blood and send it to a laboratory for analysis and results.
- Positive TB blood test: This means you’ve been infected with TB bacteria. Additional tests are needed to determine if you have latent TB infection or TB disease.
- Negative TB blood test: This means your blood did not react to the test and that latent TB infection or TB disease is not likely.
TB blood tests are the preferred TB test for:
- Patients who have already received the TB vaccine.
- A patient who may be unable to return for a second appointment to assess any reaction to the TST.
Tuberculosis Testing & Treatment At vybe
vybe urgent care offers 2 testing options for tuberculosis (TB):
Mantoux Tuberculin Skin Test (TST)
The most commonly used skin test to check for TB is the PPD (purified protein derivative).
- A vybe clinician will inject a small amount of testing fluid into the skin on the lower part of your arm.
- After 48 to 72 hours, you must return to vybe to have your skin test read by a team member.
- You may have swelling where the tuberculin was injected. If that is the case, a team member will measure the swelling and tell you if your reaction to the test is positive or negative.
- A positive reaction usually means that you have been infected by someone with TB disease. If your test returns positive for tuberculosis, it could be latent tuberculosis and not active. Because tuberculosis can be life-threatening, it’s important to receive additional testing to ensure an accurate diagnosis.
Quantiferon Gold Plus
This blood test (ISGRA) is an alternative to traditional TB skin tests that require two office visits.
The CDC recommends this test in place of a TB test for adults, but not along with. Since it’s a faster exam, it’s often the first choice of employers who need the most reliable results to verify employment. If you’ve already been vaccinated for tuberculosis ( BCG Bacillus Calmette–Guérin) or you’ve had many prior TST tests, your clinician may recommend this test for a more accurate indication of infection. Reasons your clinician may recommend using the QuantiFERON Gold Plus Test over a TB skin test (TBT or PPD) include:
- A single patient visit to conduct the test
- Results available more quickly – 24 hours
- More than 99% specific, virtually eliminating false positives.
- Provides an objective result, unaffected by reader bias.
- Prior BCG (bacille Calmette-Guérin) vaccination does not cause a false-positive IGRA test result.
- Does not boost responses measured by subsequent tests, and less affected by prior TST.
A vybe clinician will draw blood and follow the lab’s instructions to ensure your blood sample reaches the lab in the proper time frame for an accurate read.
If you receive a positive result from either test, the vybe medical team will discuss the history of your exposure to TB and determine whether your immune system has been weakened. A chest X-ray is a usual response to a positive skin test for tuberculosis. If additional testing is required outside the scope of our in-house labs, vybe will manage the referral and transfer your records as needed.
Prescriptions commonly used to treat active TB are rifampin (Rifadin, rifampicin), ethambutol (Myambutol), and pyrazinamide in conjunction with isoniazid (INH). Four drugs are often taken for the first two months of therapy to help kill any potentially resistant strains of bacteria.
If you need a tuberculosis test, for employment or based on risk of exposure, please visit your nearest vybe urgent care.