In suspected latent TB infection, what is the next step to evaluate for active disease?

• A. Chest radiograph
• B. Mantoux tuberculin skin test
• C. Sputum AFB smear
• D. TB culture

Answer: (A)

Assessing for active tuberculosis starts with a chest radiograph. In someone suspected of having latent TB infection, you want to quickly rule out active disease before labeling it latent. A chest X-ray can show signs of active pulmonary TB, such as focal consolidation, cavitation, nodular infiltrates, or effusions, which would shift management toward confirming and treating active disease. If the radiograph is normal and there are no symptoms, it’s reasonable to proceed with tests that indicate infection (Mantoux or IGRA) to assess latent infection, keeping in mind these tests don’t distinguish activity. If there are abnormalities on the radiograph or persistent suspicion, microbiologic tests like sputum AFB smear and TB culture are pursued to confirm activity; culture remains the gold standard but takes longer.