A newly hired employee cannot receive a tuberculin skin test because of a childhood BCG vaccination. What should the IP recommend?

• A. Testing with an interferon-gamma release assay (IGRA).
• B. Repeating the tuberculin skin test after 6 months.
• C. Proceed with a standard TST anyway.
• D. Do nothing and monitor for symptoms.

Answer: (A)

BCG vaccination can cause cross-reactivity with the tuberculin skin test, making TST results unreliable for someone who was vaccinated in childhood. The best move is to use an interferon-gamma release assay (IGRA), which targets TB-specific antigens not present in BCG. This makes IGRA more accurate for detecting latent TB infection in someone with prior BCG vaccination. If the IGRA is positive, follow the standard evaluation and management for latent TB; if negative, latent TB is unlikely. Repeating the TST wouldn’t fix the cross-reactivity issue and could still give misleading results, while doing nothing or waiting for symptoms misses the opportunity to properly screen a healthcare worker.