TB Test Assessment and Evaluation 3

Question 1

A QuantiFERON-TB Gold Plus (QFT-Plus) test reports TB1 and TB2 tube results. What is the significance of the TB2 tube?

Accepted Answer

It detects both CD4+ and CD8+ T-cell responses, potentially improving detection in some populations

Answer

The TB2 tube in QFT-Plus contains peptides that stimulate both CD4+ and CD8+ T-cells, potentially improving sensitivity in immunocompromised individuals.

Question 2

A nurse administers 0.1 mL of PPD tuberculin intradermally and observes a bleb of 6mm immediately after injection. What does this bleb indicate?

Accepted Answer

Correct intradermal injection technique with proper bleb formation

Answer

A pale, raised bleb of 6–10mm immediately after injection confirms correct intradermal placement of the tuberculin.

Question 3

Which of the following populations has the LOWEST positive predictive value for TST, making IGRA generally preferred?

Accepted Answer

BCG-vaccinated individuals from countries with routine infant BCG programs

Answer

BCG vaccination can cause false-positive TST results, lowering the positive predictive value; IGRA antigens (ESAT-6, CFP-10) are absent from BCG strains.

Question 4

A patient's TST placed on Monday is read on Friday (96 hours later). The result shows 12mm induration. How should this be handled?

Accepted Answer

Reject the result as invalid; repeat TST immediately at a new site

Answer

TST must be read 48–72 hours after placement; readings after 72 hours are unreliable and the test should be repeated.

Question 5

In a correctional facility outbreak investigation, a newly incarcerated individual tests positive on TST. Which factor is most important in determining whether this represents LTBI acquired inside or before incarceration?

Accepted Answer

Documentation of a negative TST at intake within the past 2 years

Answer

A documented negative TST at intake followed by a new positive establishes a conversion that likely occurred during incarceration.

(TB Test) Tuberculosis Test Certification Practice Test

(TB Test) Tuberculosis Test Certification Practice Test

TB Test Assessment and Evaluation 3