Clinical Testing Guidance for Tuberculosis: Tuberculin Skin Test Tuberculosis TB

CDC has resources to help health care providers talk to patients about TB testing and treatment. The TB skin test should be placed and read by a designated, trained health care provider. All U.S. health care personnel should be screened for tuberculosis (TB) upon hire (i.e., preplacement). Therefore, a single negative antigen test cannot rule out infection. Viral tests look for a current infection with SARS-CoV-2, the virus that causes COVID-19, by testing specimens from your nose or mouth. A positive skin test result for TB infection means you have TB germs in your body.

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Treatment for latent TB infection is 90% effective for preventing the development of TB disease. If latent TB infection is diagnosed, short and convenient treatment regimens are available. The reaction should be measured in millimeters of the induration (firm swelling). Testing for TB infection with a TB skin test can be done before, during, or after a COVID-19 vaccination visit. Vaccination with inactivated viruses doesn’t interfere with TB skin test reactions.

Testing results

Once you have a positive TB blood test or TB skin test result, you may still have a positive test result on future TB tests. A positive blood test result for TB infection means you have TB germs in your body. TB blood tests are the preferred tests for people who have received the BCG TB vaccine. NIOSH conducted a study on respirator fit over time and the results confirm the necessity of the current OSHA respirator fit testing requirement, both annually and when physical changes have occurred.

Healthcare-specific information

• Your doctor will recommend a re-testing schedule based on your age and risk factors.
• See FDA’s list of In Vitro Diagnostics Emergency Use Authorizations for more information about the performance and interpretation of specific authorized tests.
• Consult with your state and local public health authorities to determine who is authorized to place and read TB skin tests in your state.
• There are companies and organizations that provide training on performing a fit test.
• A positive skin test result for TB infection means you have TB germs in your body.

Anyone who tests positive should take steps to prevent spreading COVID-19 to others or, if in a healthcare setting, be placed on appropriate precautions. Positive test results using a viral test (NAAT, antigen or other tests) in individuals with signs or symptoms consistent with COVID-19 indicate that the person has COVID-19. Health care personnel with a documented history of a prior positive TB test result should receive an individual TB risk assessment and TB symptom screen upon hire (i.e., pre-placement). If you used an antigen test, follow FDA recommendations for repeat testing. A negative COVID-19 test means the Bangla Bet test did not detect the virus, but this doesn’t rule out that you could have an infection. A positive COVID-19 test means the virus was detected and you have or recently had an infection.

It takes 2 to 8 weeks after initial infection with TB bacteria for the immune system to be able to react to PPD and for the infection to be detected by the TB skin test. PPD is diluted to standard concentration and potency in FDA-approved testing solutions. Typically, PPD produces a T-cell mediated delayed-type hypersensitivity reaction if the person has been infected with TB bacteria. Efforts should be made to address barriers that might overtly or inadvertently create inequalities in testing. Delays in testing may also delay seeking care and treatment (when sick) as well as delays in prevention measures that could reduce the spread of the virus to others.