| Tuberculosis Exams and Tests | | | | is an aid in the diagnosis of TB. This test can help |
| The doctor will complete the following tests to | | | | detect active and latent tuberculosis. The body |
| diagnose tuberculosis. You may not be hospitalized | | | | responds to the presence of the tuberculosis |
| for either the initial tests or the beginning of | | | | bacteria. By special techniques, the patient's blood is |
| treatment. | | | | incubated with proteins from TB bacteria. If the |
| Chest X-ray: The most common diagnostic test that | | | | bacteria is in the patient, the immune cells in the |
| leads to the suspicion of infection is a chest X-ray. | | | | blood sample respond to these proteins with the |
| In primary TB, an X-ray will show an abnormality in | | | | production of a substance called interferon-gamma |
| the mid and lower lung fields, and lymph nodes may | | | | (IFN-gamma). This substance is detected by the test. |
| be enlarged. | | | | If someone had a prior BCG vaccination (a vaccine |
| Reactivated TB bacteria usually infiltrate the upper | | | | against TB given in some countries but not the U.S.) |
| lobes of the lungs. | | | | and a positive skin test due to this, the |
| Miliary tuberculosis exhibits diffuse nodules. | | | | QuantiFERON-TB Gold test will not detect any |
| Mantoux skin test also known as a tuberculin skin | | | | IFN-gamma. |
| test (TST): This test helps identify people infected | | | | Sputum testing: Sputum testing for acid-fast bacilli is |
| with M. tuberculosis but who have no symptoms. A | | | | the only test that confirms a TB diagnosis. If sputum |
| doctor must read the test. | | | | (the mucus you cough up) is available, or can be |
| The doctor will inject 5 units of purified protein | | | | induced, a lab test may give a positive result in up to |
| derivative (PPD) into your skin. If a raised bump of | | | | 30% of people with active disease. |
| more than 5 mm (0.2 in) appears at the site 48 hours | | | | Sputum or other bodily secretions such as from your |
| later, the test may be positive. | | | | stomach or lung fluid can be cultured for growth of |
| This test can often indicate disease when there is | | | | mycobacteria to confirm the diagnosis. |
| none (false positive). Also, it can show no disease | | | | It may take one to three weeks to detect growth in |
| when you may in fact have TB (false negative). | | | | a culture, but eight to 12 weeks to be certain of the |
| QuantiFERON-TB Gold test: This is a blood test that | | | | diagnosis. |