Which TB test is preferred for higher specificity in screening?

Which TB test is preferred for higher specificity in screening?

• A. Sputum culture
• B. IGRAs (QuantiFERON-TB Gold Plus, T-SPOT)
• C. Chest X-ray
• D. Mantoux skin test

Answer: (B)

The main idea is choosing a screening test with the fewest false positives. Interferon-gamma release assays (IGRAs), such as QuantiFERON-TB Gold Plus or T-SPOT.TB, use TB-specific antigens not present in most BCG vaccines or many non-tuberculous mycobacteria. Because of this, they have higher specificity than the Mantoux tuberculin skin test, particularly in people who have received the BCG vaccine or have prior mycobacterial exposure. That means fewer people are incorrectly labeled as infected when screening. Sputum culture is highly specific but is used to confirm active TB rather than for broad screening and requires symptoms and laboratory processing. Chest X-ray can hint at TB but is not specific enough to diagnose infection. The Mantoux skin test is inexpensive and easy but can yield false positives due to prior BCG vaccination or NTM exposure, reducing specificity. So, for screening with the goal of higher specificity, IGRA tests are preferred.

The main idea is choosing a screening test with the fewest false positives. Interferon-gamma release assays (IGRAs), such as QuantiFERON-TB Gold Plus or T-SPOT.TB, use TB-specific antigens not present in most BCG vaccines or many non-tuberculous mycobacteria. Because of this, they have higher specificity than the Mantoux tuberculin skin test, particularly in people who have received the BCG vaccine or have prior mycobacterial exposure. That means fewer people are incorrectly labeled as infected when screening.

Sputum culture is highly specific but is used to confirm active TB rather than for broad screening and requires symptoms and laboratory processing. Chest X-ray can hint at TB but is not specific enough to diagnose infection. The Mantoux skin test is inexpensive and easy but can yield false positives due to prior BCG vaccination or NTM exposure, reducing specificity. So, for screening with the goal of higher specificity, IGRA tests are preferred.