After a recent tuberculosis exposure, a healthcare worker has a 15 mm positive TST but no symptoms. What is the significance and recommended follow-up?

• A. Active TB disease; start treatment immediately.
• B. Latent TB infection (LTBI); administer prophylaxis and obtain baseline chest X-ray.
• C. No infection; retest in one year.
• D. Need chest X-ray only; no treatment necessary.

Answer: (B)

A recent TB exposure with a positive tuberculin skin test in a person with no symptoms indicates infection with TB bacteria, but not active disease. The appropriate action is to treat latent TB infection to prevent progression to active TB, while also ruling out active disease with a baseline chest X-ray. Starting LTBI treatment reduces the risk that the infection becomes active later, which is especially important for healthcare workers who could spread TB to others. The baseline chest X-ray helps ensure there is no existing active TB before beginning preventive therapy. If there were symptoms such as persistent cough, fever, night sweats, or weight loss, or if the chest X-ray showed concerning findings, the approach would shift toward evaluating for and treating possible active TB.