TB Test Assessment and Evaluation 2

Question 1

A patient with a 14mm induration on TST has no risk factors and was born in a low-prevalence country. How should this result be interpreted?

Accepted Answer

Negative — threshold for low-risk individuals is 15mm

Answer

For persons with no known risk factors in low-prevalence settings, the positive threshold is ≥15mm induration.

Question 2

Which IGRA result pattern indicates a borderline or indeterminate finding that requires retesting?

Accepted Answer

IFN-γ nil ≥8 IU/mL causing invalid background

Answer

An indeterminate IGRA result occurs when the nil tube IFN-γ is excessively elevated (≥8 IU/mL), invalidating the test.

Question 3

A chest X-ray shows upper lobe fibrotic changes in a patient with a positive TST. What is the most appropriate next step?

Accepted Answer

Order sputum smear and culture to rule out active TB

Answer

Fibrotic upper lobe changes on CXR in a TST-positive patient raise concern for active or prior TB, requiring microbiologic evaluation.

Question 4

During a TB contact investigation, which classification describes a person exposed to an infectious TB case who has a negative TST but should be retested in 8–10 weeks?

Accepted Answer

Window period contact

Answer

Window period contacts had recent exposure and may not yet have mounted a detectable immune response, so retesting after the window period is required.

Question 5

Which of the following conditions can cause a false-negative TST result despite true LTBI?

Accepted Answer

Advanced HIV infection with CD4 count <200 cells/µL

Answer

Severe immunosuppression such as advanced HIV reduces T-cell response, causing anergy and false-negative TST results.

(TB Test) Tuberculosis Test Certification Practice Test

(TB Test) Tuberculosis Test Certification Practice Test

TB Test Assessment and Evaluation 2