TB Test Assessment and Evaluation 4

Question 1

Which chest X-ray finding in a TB-exposed, TST-positive patient is MOST consistent with primary TB infection in childhood rather than reactivation TB?

Accepted Answer

Ghon complex with calcified hilar lymph nodes

Answer

Bilateral upper lobe cavitary infiltrates

Answer

Miliary pattern with diffuse nodules throughout both lungs

Answer

Pleural effusion with lower lobe consolidation

Question 2

A serial TST program documents a healthcare worker's TST increasing from 0mm to 10mm over a 2-year period. CDC defines TST conversion as:

Accepted Answer

Any increase of ≥5mm in TST induration within a 2-year period

Answer

An increase of ≥10mm in TST induration within a 2-year period

Answer

Any new positive result regardless of prior reading

Answer

An increase from negative to any measurable induration

Question 3

Which of the following correctly describes the T-SPOT.TB assay methodology?

Accepted Answer

Peripheral blood mononuclear cells are isolated and spot-forming cells counted via ELISPOT

Answer

Whole blood is incubated with TB antigens and plasma IFN-γ is measured by ELISA

Answer

T lymphocytes are stained for intracellular IFN-γ by flow cytometry

Answer

Serum antibodies against PPD are quantified by chemiluminescent immunoassay

Question 4

A school-aged child with no risk factors has a TST of 8mm induration. What is the correct interpretation per CDC guidelines?

Accepted Answer

Negative — the threshold for low-risk individuals is ≥15mm

Answer

Positive — children under 18 use a lower 5mm threshold

Answer

Positive — the threshold for school children is ≥10mm

Answer

Indeterminate — children require IGRA confirmation

Question 5

During TST administration, the nurse inadvertently injects the tuberculin subcutaneously. What is the appropriate action?

Accepted Answer

Document the error, do not retest the same site, and repeat at a new site after 1 week

Answer

Read the site at 72 hours regardless of injection depth

Answer

Immediately apply pressure and massage to disperse the tuberculin

Answer

Administer a second intradermal injection at an adjacent site on the same arm

Question 6

A foreign-born patient from a high-TB-incidence country has a positive IGRA. Chest X-ray is normal and the patient is asymptomatic. What is the most appropriate next step?

Accepted Answer

Evaluate for LTBI and discuss treatment with isoniazid, rifapentine, or rifampin

Answer

Initiate four-drug active TB treatment immediately

Answer

Repeat IGRA in 3 months to confirm the result before any action

Answer

No action needed — IGRA positivity in foreign-born individuals is expected

Question 7

When counseling a patient about TB testing results, which statement most accurately explains the difference between LTBI and active TB?

Accepted Answer

LTBI means the bacteria are dormant and the person is not infectious, while active TB means the bacteria are multiplying and can be transmitted

Answer

LTBI and active TB are both infectious and require identical treatment regimens

Answer

Active TB only occurs in HIV-positive patients, while LTBI occurs in immunocompetent individuals

Answer

LTBI is detected only by TST, while active TB is detected only by sputum culture