A 32-year-old woman from a high TB prevalence country with BCG vaccination and a PPD of 12 mm has which risk status and recommended next step?

• A. High risk; isoniazid therapy
• B. Low risk; observation
• C. Moderate risk; chest X-ray
• D. High risk; rifampin therapy first

Answer: (A)

Interpreting a tuberculin skin test in someone from a country with high TB prevalence is about recognizing when a positive result indicates latent infection rather than active disease. In populations at high risk, an induration of 10 mm or more is considered positive; in this case, a 12 mm reaction is positive despite prior BCG vaccination, because the risk context (origin from a high-prevalence area) makes a positive test meaningful for latent infection rather than a false positive from vaccination alone.

A person with a positive test but no symptoms or signs of active TB should first have a chest radiograph to exclude active disease. If the radiograph is normal and there are no clinical signs of active TB, the appropriate management is treatment for latent TB infection to prevent progression to active TB. The standard approach is isoniazid therapy for several months (traditionally about 9 months), with monitoring for adherence and potential hepatotoxicity.

So, this scenario describes a high risk status with latent TB infection, for which isoniazid therapy is the recommended next step after ruling out active disease.