TB Test Diagnostic Approaches 2 — Questions and Answers
Question 1: Which imaging finding on chest X-ray is most characteristic of primary TB infection in children?
- Hilar lymphadenopathy (Correct answer)
- Pleural effusion only
- Miliary nodules
- Cavitary lesion in upper lobe
Correct answer: Hilar lymphadenopathy
Primary TB in children commonly presents with hilar or mediastinal lymphadenopathy, often more prominent than the parenchymal lesion itself.
Question 2: What is the recommended minimum number of sputum specimens for AFB smear microscopy in suspected pulmonary TB?
- 1 specimen
- 2 specimens (Correct answer)
- 3 specimens
- 5 specimens
Correct answer: 2 specimens
CDC and WHO guidelines recommend at least 2 sputum specimens collected at least 8 hours apart, including one early morning sample, to maximize sensitivity.
Question 3: A patient with suspected TB has a negative sputum smear but positive nucleic acid amplification test (NAAT). What is the most appropriate next step?
- Repeat smear microscopy only
- Initiate TB treatment based on NAAT result (Correct answer)
- Discard results and wait for culture
- Perform only tuberculin skin test
Correct answer: Initiate TB treatment based on NAAT result
A positive NAAT in a smear-negative patient with clinical suspicion for TB warrants initiating treatment, as NAAT is highly specific for M. tuberculosis.
Question 4: Which of the following best describes the concept of 'two-step TST testing'?
- Performing TST on two separate body sites simultaneously
- Repeating TST 1-3 weeks after an initial negative to detect boosting (Correct answer)
- Reading TST results at both 48 and 72 hours
- Using two different tuberculin antigens
Correct answer: Repeating TST 1-3 weeks after an initial negative to detect boosting
Two-step TST involves performing a second TST 1-3 weeks after a negative initial test to distinguish boosting of waned immunity from true conversion in baseline testing programs.
Question 5: When is CT chest preferred over standard chest X-ray in TB diagnosis?
- In all patients with suspected TB
- When X-ray is normal but clinical suspicion remains high (Correct answer)
- Only for smear-positive patients
- As a routine follow-up test after treatment
Correct answer: When X-ray is normal but clinical suspicion remains high
CT chest provides superior sensitivity for detecting subtle parenchymal disease, lymphadenopathy, or early cavitation when standard X-ray appears normal but TB is still clinically suspected.
Question 6: Which specimen collection method yields the highest sensitivity for diagnosing pulmonary TB in patients who cannot produce sputum?
- Throat swab
- Nasopharyngeal aspirate
- Bronchoscopy with BAL (Correct answer)
- Blood culture only
Correct answer: Bronchoscopy with BAL
Bronchoscopy with bronchoalveolar lavage (BAL) allows direct sampling from the lower respiratory tract and has higher sensitivity than induced sputum in patients unable to expectorate.
Question 7: What does a 'positive' IGRA result indicate in a low-risk asymptomatic individual?
- Active TB disease requiring immediate treatment
- M. tuberculosis infection (latent or active) requiring further evaluation (Correct answer)
- BCG vaccination effect
- Non-specific immune response unrelated to TB
Correct answer: M. tuberculosis infection (latent or active) requiring further evaluation
A positive IGRA indicates immune sensitization to M. tuberculosis antigens, meaning the person has been infected, but further clinical evaluation is needed to distinguish latent TB from active disease.
TB Test Diagnostic Approaches 2
Which imaging finding on chest X-ray is most characteristic of primary TB infection in children?