Management of Asymptomatic TB-Exposed Child with Positive PPD
This 7-year-old child with a 14mm PPD induration after TB exposure requires TB prophylaxis (Option B) after active disease is excluded.
Immediate Next Steps
The child should undergo chest radiography to exclude active TB disease before initiating treatment for latent TB infection. 1, 2 In children with known TB exposure and a positive PPD (≥5mm induration), the priority is ruling out active disease through clinical evaluation and chest X-ray. 1
Rationale for TB Prophylaxis
A 14mm induration is definitively positive in this context. For children who are close contacts of infectious TB cases, ≥5mm induration is considered positive. 1, 2 This child far exceeds that threshold at 14mm. 3
Children under age 5 are at highest risk for progression to severe TB disease, making prophylaxis particularly critical. 1 While this child is 7 years old, they still fall within the pediatric high-risk category (children <15 years). 1
Close contacts of newly diagnosed infectious TB with ≥5mm induration are explicit candidates for preventive therapy. 3 The FDA label for isoniazid specifically lists "close contacts of persons with newly diagnosed infectious tuberculosis (≥5mm)" as indication for prophylaxis. 3
Why Not the Other Options?
Empirical 4-drug anti-TB treatment (Option A) is inappropriate because the child is asymptomatic and has no evidence of active disease. 1 Four-drug regimens are reserved for active TB disease, not latent infection. 1
IGRA testing (Option C) is unnecessary because the PPD is already definitively positive at 14mm. 2 IGRA might be considered when PPD results are equivocal or to avoid the booster phenomenon, but this child has clear-cut TB infection requiring action, not additional testing. 2
Treatment Regimen
Standard prophylaxis is isoniazid for 9 months for most children with latent TB infection. 1, 3, 4
Alternative: 4 months of rifampin can be used if isoniazid is contraindicated. 1, 3
The child must have active TB excluded by chest radiograph and clinical evaluation before starting prophylaxis. 1, 2 Any symptoms (cough >3 weeks, fever, weight loss, night sweats) would require full diagnostic workup including sputum studies if feasible. 1
Critical Pitfalls to Avoid
Do not delay prophylaxis waiting for symptoms to develop. Children can progress rapidly from infection to disease, particularly those under 5 years. 1, 5 This 7-year-old still warrants urgent intervention.
Do not assume a negative chest X-ray rules out infection. The PPD is the definitive test for TB infection; chest X-ray only rules out active disease. 1, 6
Monitor for hepatotoxicity during isoniazid therapy, especially checking liver function tests every 2-4 weeks and monitoring for clinical symptoms (nausea, vomiting, jaundice). 1
Ensure completion of the full 9-month course. Incomplete treatment increases risk of progression to active disease. 3, 6