From the Guidelines
No, a TB skin test should not be taken on a patient with a prior positive result, as it can lead to a severe skin reaction and is not necessary for diagnosis. The TB skin test, also known as the tuberculin skin test (TST), is used to diagnose latent tuberculosis infection (LTBI) 1. However, once a person has had a positive TB skin test, they will likely always test positive, even if they've been treated for TB infection 1. This is because the test detects the immune system's reaction to TB proteins, which remains present after infection. For patients with a documented history of a positive TB skin test, alternative testing methods such as an interferon-gamma release assay (IGRA) blood test should be used instead 1. Additionally, these patients should undergo a chest X-ray to rule out active TB disease. Some key points to consider when dealing with patients who have had a prior positive TB skin test include:
- The patient's medical record should clearly document their positive TB skin test history to prevent unnecessary repeat testing 1.
- Repeat testing is not recommended for patients with a prior positive result, unless they have been treated for TB infection and are being retested to confirm cure 1.
- Patients with advanced HIV disease who initially had negative TST or IGRA results but subsequently experienced an increase in the CD4 cell count to >200 cells/µL on ART may require repeat testing 1. It's also important to note that the sensitivity of the TST is high (95%–98%) in clinically well persons with previously treated tuberculosis 1. However, false-negative reactions can occur in certain situations, such as in infants and young children, early after infection, or in persons with immunosuppression 1.
From the Research
TB Skin Test on Patients with Prior Positive
- There is no direct evidence in the provided studies to suggest that a TB skin test cannot be taken on a patient with a prior positive result.
- The studies primarily focus on the treatment of tuberculosis, including drug regimens and their efficacy, rather than the administration of TB skin tests 2, 3, 4, 5, 6.
- None of the studies mention any contraindications or precautions for administering a TB skin test to patients with a history of positive results.
- It is essential to consult additional resources or guidelines specific to TB skin testing to determine the appropriate procedure for patients with prior positive results.