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3. Testing for Infection
The third component of the medical evaluation is testing for TB infection. As discussed in Lesson 3, these diagnostic tests can be used to detect infection with M. tuberculosis. Patients with symptoms of TB disease may be given a TB blood test or TB skin test.
A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection 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.
Patients with symptoms of TB disease should always be evaluated for TB disease, regardless of their test results.
Additionally, if a patient has symptoms of TB disease, clinicians should not rely on or wait for these test results before ordering a chest x-ray and other diagnostic tests (for example, bacteriological examination).
