Management of a 7-Year-Old with Positive PPD and Household TB Exposure
Give chemoprophylaxis for latent TB infection (Option A) with isoniazid for 9 months. This child has latent TB infection based on a PPD of 14 mm with known household exposure to active TB, and the negative chest X-ray confirms absence of active disease. 1, 2
Rationale for This Recommendation
The PPD result of 14 mm is definitively positive in this clinical context. For close contacts of persons with newly diagnosed infectious tuberculosis, a PPD induration ≥5 mm is considered positive. 2 This child exceeds that threshold nearly threefold, making the diagnosis of latent TB infection certain. 3
Active TB has been appropriately ruled out. The negative chest radiograph excludes pulmonary tuberculosis, which is the most common form in children. 3 Patients with positive skin tests should be evaluated with chest radiography to exclude active disease before initiating treatment for latent infection. 3
Why Not the Other Options
IGRA testing (Option B) is unnecessary and would delay treatment. The PPD is already definitively positive in a high-risk contact, and IGRA would not change management. 2 The child meets clear criteria for latent TB treatment based on PPD alone: close contact with infectious TB and ≥5 mm induration. 2
Treatment for active TB (Option C) is inappropriate. Active tuberculosis requires clinical or radiographic evidence of disease. 3 This child has no symptoms mentioned and a normal chest X-ray. In one recent U.S. study of 485 children with positive PPD, only 0.2% had active disease requiring treatment. 4
Specific Treatment Protocol
Isoniazid 300 mg daily (or 10-15 mg/kg/day, maximum 300 mg) for 9 months is the preferred regimen. This provides maximal benefit in preventing progression to active TB and is superior to 6 months of treatment. 1, 2 For a 7-year-old, the weight-based dosing would typically be 10-15 mg/kg/day as a single daily dose. 2
Alternative regimen: Rifampin 600 mg daily for 4 months can be used if isoniazid toxicity is a concern, though this is typically reserved for specific situations. 1
Critical Monitoring Requirements
Obtain baseline liver function tests before starting therapy. Although the child is under 35 years old, baseline testing is prudent given the 9-month treatment duration. 1
Conduct monthly clinical assessments to evaluate for symptoms of hepatotoxicity including nausea, vomiting, jaundice, and abdominal pain. 1 Educate the family to stop medication immediately and seek care if these symptoms develop. 1
Withhold isoniazid if transaminases exceed 3 times the upper limit of normal with symptoms or 5 times without symptoms. 1
Important Clinical Caveats
Children under 4 years old are at highest risk for disseminated TB including life-threatening meningeal disease, making treatment particularly important in this age group. 5, 6 While this child is 7 years old, the principle underscores the importance of not delaying treatment in pediatric contacts.
Do not delay treatment while pursuing additional testing. The diagnosis is clear, and postponing chemoprophylaxis increases the risk of progression to active disease. 5
BCG vaccination history, if present, does not change this recommendation. A PPD induration >14 mm is unlikely to be due to prior BCG vaccination alone, especially in a child with documented TB exposure. 3, 7