Which statement about TB testing is true?

• A. A positive TST confirms active TB disease
• B. A positive TST indicates infection; further testing is needed to determine latent or active
• C. A negative TST rules out TB infection
• D. There is no need for further testing after a positive TST if the patient is asymptomatic

Answer: (B)

Tuberculin skin testing detects exposure to TB and the body's immune response, not whether the bacteria are actively causing disease. A positive test means infection has occurred, but it doesn’t distinguish latent TB infection from active TB disease. To tell the difference, you need to assess symptoms and perform further evaluation such as a chest radiograph and microbiologic tests (sputum smear and culture or rapid NAAT). That’s why the statement describing a positive test as indicating infection and requiring additional testing to determine latent versus active is the correct one.

A negative test, especially in someone with recent exposure or who is immunocompromised, does not completely rule out infection. And even if a patient is asymptomatic, a positive TST still prompts evaluation to rule out active disease and to consider treatment for latent infection if indicated.