Which statement about latent TB tests (TST or IGRA) is true?

• A. They diagnose active TB with high specificity
• B. They replace chest radiography for active TB
• C. They detect HIV infection
• D. They test for latent TB infection and cannot distinguish latent from active disease

Answer: (B)

Latent TB tests are designed to detect prior TB infection, not current disease. A positive TST or IGRA indicates you have been infected at some point, but it does not prove that TB is active now. Diagnosing active TB relies on symptoms, chest imaging, and microbiologic confirmation (such as sputum smear, culture, or molecular tests). Chest radiography helps evaluate possible active TB, but it does not replace microbiology for a definitive diagnosis. These tests do not detect HIV infection. So the true statement is that they test for latent TB infection and cannot distinguish latent from active disease.