Which test is commonly used to screen for latent tuberculous infection?

Which test is commonly used to screen for latent tuberculous infection?

• A. Mantoux tuberculin skin test (TST) or IGRA
• B. Chest X-ray
• C. Sputum smear
• D. PCR for Mycobacterium tuberculosis

Answer: (A)

Screening for latent tuberculosis infection relies on tests that detect immune sensitization to TB antigens, indicating prior infection without active disease. The Mantoux tuberculin skin test and interferon-gamma release assays (IGRAs) are used for this purpose because they measure the immune system’s memory of TB exposure. They do not diagnose active TB, which is why a positive result leads to further evaluation to rule out active disease. In contrast, chest X-ray is mainly used to assess for signs of active pulmonary TB, and sputum smear or PCR for Mycobacterium tuberculosis detects bacteria or bacterial DNA in respiratory samples, signaling active infection. Hence, the commonly used screen for latent TB infection is the Mantoux TST or IGRA.

Screening for latent tuberculosis infection relies on tests that detect immune sensitization to TB antigens, indicating prior infection without active disease. The Mantoux tuberculin skin test and interferon-gamma release assays (IGRAs) are used for this purpose because they measure the immune system’s memory of TB exposure. They do not diagnose active TB, which is why a positive result leads to further evaluation to rule out active disease. In contrast, chest X-ray is mainly used to assess for signs of active pulmonary TB, and sputum smear or PCR for Mycobacterium tuberculosis detects bacteria or bacterial DNA in respiratory samples, signaling active infection. Hence, the commonly used screen for latent TB infection is the Mantoux TST or IGRA.