From the Guidelines
A TB skin test will typically become positive 8 to 10 weeks after exposure to tuberculosis bacteria. This timeframe is crucial in determining the accuracy of the test results, as testing too early after exposure may yield false negative results 1.
Key Considerations
- The body needs time to develop an immune response that can be detected by the test, which is why a follow-up test is usually recommended 8-10 weeks after the last exposure.
- The test works by injecting a small amount of tuberculin protein under the skin, causing a visible reaction in people whose immune systems recognize the protein from previous TB exposure.
- A positive test indicates infection with TB bacteria, not necessarily active disease, and further evaluation, including chest X-rays and possibly sputum tests, would be needed to determine if active tuberculosis is present 1.
Important Details
- Contacts with initially negative tuberculin skin test results should receive treatment for LTBI after TB disease has been ruled out by clinical examination and chest radiograph, especially if they are younger than 5 years, have HIV infection, or are otherwise immunocompromised 1.
- If the second skin test result is negative, treatment for LTBI may be discontinued, and further follow-up is unnecessary, unless the contact is immunocompromised or remains in close contact with an infectious patient 1.
From the Research
TB Skin Test Positivity After Exposure
- The provided studies do not directly address when a TB skin test will be positive after exposure 2, 3, 4, 5, 6.
- However, it is known that the TB skin test, also known as the Mantoux test, measures the response of the immune system to the presence of TB bacteria 2.
- The test typically becomes positive 4-6 weeks after infection, but this can vary depending on several factors, such as the individual's immune status and the severity of the infection.
- The studies provided focus on the treatment of latent tuberculosis infection and the comparison of different treatment regimens, rather than the timing of TB skin test positivity after exposure 3, 4, 5, 6.
- Therefore, there is limited information available from these studies to answer the question of when a TB skin test will be positive after exposure.