tuberculosis-screening
Reviewed
A tuberculosis (TB) screening test checks to see if you have the bacteria that cause TB in your body. It cannot tell whether the infection is active or inactive. To diagnose TB, your provider must review your medical history, symptoms, and possibly other tests.
Preparation and collection
You don't need any special preparations for a TB skin or blood test.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- A positive screening result does not diagnose active or inactive TB; further testing is required.
- False positives can occur, especially if you have had the BCG TB vaccine or an infection from a related bacterium.
- False negatives can occur if you contracted TB within the past 8–10 weeks or have had certain measles or smallpox vaccines.
- TB blood tests are more accurate than TB skin tests overall.
- Your provider will consider your health history and risk factors when interpreting results.
What to do next
If your test is positive, you will need more tests (such as a chest x-ray or sputum culture) to determine if you have inactive TB infection or active TB disease. If your test is borderline, you will likely be tested again. Both active TB disease and inactive TB infections should be treated with antibiotics. Treatment may last a few months to a year. Stopping treatment too soon can cause the infection to come back and make it harder to treat.