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

Newly developed interferon-gamma release assays have become commercially available to detect tuberculosis (TB) infection in adults. However little is known about their performance in children. We compared test results between the QuantiFERON-TB Gold test (QFT) and tuberculin skin test (TST) in young children living with pulmonary TB patients in Cambodia. Of 195 children tested with both QFT and TST the TST-positive rate of 24% was significantly higher than the QFT-positive rate of 17%. The agreement between the test results was considerable (kappa-coefficient 0.63). Positive rates increased from 6% to 32% for QFT and from 15% to 43% for TST according to the sputum smear grades of the index cases. The presence of Bacille Calmette-Guerin (BCG) scars did not significantly affect the results of TST or QFT in a logistic regression analysis. In conclusion QFT can be a substitute for TST in detecting latent TB infection in childhood contacts aged BCG vaccination or non-tuberculous mycobacterial infection.