TB Test Core Knowledge and Fundamentals 3

Question 1

A healthcare worker's TST shows 8 mm induration. She has no risk factors and has received BCG vaccine. How should this result be interpreted?

Accepted Answer

Negative — the cutoff for healthcare workers is ≥10 mm

Answer

For healthcare workers without other risk factors, ≥10 mm induration is considered positive; 8 mm falls below that threshold.

Question 2

Which IGRA test measures interferon-gamma release in response to ESAT-6 and CFP-10 antigens?

Accepted Answer

QuantiFERON-TB Gold Plus (QFT-Plus)

Answer

QFT-Plus and T-SPOT.TB are IGRA blood tests that detect IFN-γ released by sensitized T cells in response to M. tuberculosis–specific antigens.

Question 3

A person with HIV has a TST result of 4 mm. This is classified as:

Accepted Answer

Negative

Answer

For people living with HIV, ≥5 mm induration is positive; 4 mm does not meet that threshold and is classified negative.

Question 4

What does a 'booster effect' mean in two-step TST testing?

Accepted Answer

A larger positive reaction on the second test due to immune memory stimulated by the first test

Answer

The booster effect occurs when an initial TST stimulates immune memory so a second test weeks later gives a larger (boosted) reaction, not a new infection.

Question 5

Which of the following is a contraindication to the Mantoux TST?

Accepted Answer

Documented previous severe reaction (vesiculation, necrosis) to TST

Answer

A prior severe reaction (vesiculation, ulceration, or necrosis) to TST is a contraindication to repeat testing.

(TB Test) Tuberculosis Test Certification Practice Test

(TB Test) Tuberculosis Test Certification Practice Test

TB Test Core Knowledge and Fundamentals 3