Tuberculosis (TB) - Exams and Tests
Diagnosing active TB in the lungs
Doctors diagnose active
tuberculosis (TB) in the lungs (pulmonary TB) by using
a medical history and physical exam, and by checking
your symptoms (such as an ongoing cough, fatigue, fever, or night sweats).
Doctors will also look at the results of a:
Diagnosing latent TB in the lungs
- A tuberculin skin test will show if you have ever had a
TB infection. See a picture of a
tuberculin skin test .
- Rapid blood tests help detect latent TB.3 They can help diagnose TB when results from a tuberculin skin
test are uncertain. These tests also can tell if a person who has had a
BCG vaccination has a TB infection. A rapid test
requires only one visit to the doctor or clinic, instead of two visits as
required for the tuberculin skin test. Rapid blood tests are also called interferon-gamma release assays (IGRAs).
Diagnosing TB outside the lungs
Diagnosing TB in
other parts of the body (extrapulmonary TB) requires more
testing. Tests include:
- Biopsy. A sample of the affected area is taken out
and sent to a lab to look for
- Urine culture. This test looks for TB infection in the kidneys
- Cerebrospinal fluid test. A sample of fluid around the spine is taken to look for a TB infection in the brain (TB
- CT scan. This test is used to diagnose TB that has spread throughout the
body (miliary TB) and to detect lung cavities caused by TB.
- MRI. This test looks for TB in the brain or the
HIV infection is often done at the time of TB
diagnosis. You may also have a blood test for
Tests during TB treatment
a sputum culture is done once a month-or more often-to
make sure that the antibiotics are working. You may have a chest X-ray at the end of
treatment to use as a comparison in the future.
You may have tests
to see if TB medicines are harming other parts of your body. These tests may
Public health officials encourage
early testing for people who are at risk for getting TB.