Performance of an interferon-gamma release assay for diagnosing latent tuberculosis infection in children

Area of Science:

• Infectious Diseases
• Pediatric Medicine
• Immunology

Background:

• Interferon-gamma release assays (IGRAs) like QuantiFERON-TB Gold (QFT) are now available for tuberculosis (TB) detection in adults.
• Limited data exists on IGRA performance in pediatric populations.
• Tuberculosis remains a significant global health concern, particularly in developing countries.

Purpose of the Study:

• To compare the performance of QuantiFERON-TB Gold (QFT) and tuberculin skin test (TST) in children exposed to infectious pulmonary TB.
• To evaluate the utility of QFT as a substitute for TST in young children, specifically those under 5 years old.

Main Methods:

• A comparative study involving 195 children in Cambodia who were contacts of pulmonary TB patients.
• Both QuantiFERON-TB Gold (QFT) and tuberculin skin test (TST) were administered to all participants.
• Logistic regression analysis was used to assess factors influencing test results, including BCG vaccination scars.

Main Results:

• The TST showed a significantly higher positive rate (24%) compared to QFT (17%).
• A considerable agreement was observed between QFT and TST results (kappa-coefficient 0.63).
• Positive test rates for both QFT and TST increased with higher sputum smear grades of the index TB cases. BCG scars did not significantly impact test results.

Conclusions:

• QuantiFERON-TB Gold (QFT) is a viable alternative to the tuberculin skin test (TST) for diagnosing latent TB infection in children under 5 years old.
• QFT may be particularly useful in BCG-vaccinated children or those potentially misdiagnosed by TST due to non-tuberculous mycobacterial infections.
• This finding supports the use of IGRAs for improved TB screening in pediatric contact investigations.