After a TB exposure test indicates exposure, which follow-up tests are commonly used to evaluate for active infection?

• A. Chest X-ray and sputum culture
• B. Complete blood count only
• C. Urinalysis
• D. ECG

Answer: (A)

When a TB exposure test indicates exposure, the goal is to determine if active tuberculosis is present rather than just latent infection. The combination most commonly used to evaluate for active disease includes imaging and microbiologic confirmation. A chest X-ray screens for signs of active pulmonary TB, such as characteristic infiltrates, nodules, or cavitation, which suggest active infection. To confirm and characterize the infection, a sputum culture is performed to detect Mycobacterium tuberculosis; this not only confirms active bacteria but also allows testing for drug susceptibility to guide treatment.

Other routine tests like a complete blood count, urinalysis, or ECG don’t specifically detect active TB and aren’t used to diagnose TB, though they might be obtained for unrelated reasons.