Tuberculosis Screening in Children with BCG Vaccination History

Rationale for IGRA Testing

• The Centers for Disease Control and Prevention recommends QuantiFERON-TB Gold as an alternative to TST due to its higher specificity, single patient visit requirement, and lack of interference from prior BCG vaccination 1
• IGRAs are preferred over tuberculin skin test (TST) in patients with prior BCG vaccination because they have higher specificity and eliminate false-positive results caused by cross-reaction with BCG vaccines 2, 3

Patient Risk Factors

• This child has two key risk factors warranting TB screening: family history of latent TB and recent immigration from a high TB-burden country 4, 5

Advantages of IGRA Over TST

• IGRA measures interferon-gamma release in response to M. tuberculosis-specific antigens that are not found in BCG vaccines, providing greater specificity 6
• IGRAs eliminate reader bias and errors associated with TST placement and reading, and do not trigger an anamnestic response (boosting) 1

Diagnostic Approaches

• Tuberculin skin test is less specific in BCG-vaccinated individuals, leading to false-positive results 7, 3
• Nucleic acid amplification test is primarily used for diagnosing active TB disease, not for latent TB screening 2
• Chest radiograph is used to rule out active TB after a positive screening test, not as a primary screening tool 5

Guideline Recommendations

• The American College of Rheumatology and other guidelines specifically note that IGRA is preferred if a patient has a history of BCG vaccination 8

Follow-up Actions

• If the IGRA is positive, a chest radiograph should be performed to rule out active TB disease 9, 5
• If latent TB is confirmed, appropriate treatment for latent TB infection should be initiated according to guidelines 5
• Family members should also be evaluated for TB infection given the grandfather's history of latent TB 4