Tuberculin skin test and QuantiFERON® assay in young children investigated for tuberculosis in South Africa

SETTING: Although the literature on interferon-gamma release assays on tuberculosis (TB) in children has increased, data pertaining to young children remain relatively limited. OBJECTIVE: To compare results from the tuberculin skin test (TST) and the QuantiFERON (R)-TB Gold InTube assay (QFT) in children aged <3 years investigated for TB disease. DESIGN: TB suspects were evaluated by medical history and examination, TST, QFT, chest radiography, induced sputum and gastric washings for smear and culture for Mycobacterium tuberculosis. RESULTS: A total of 400 children were enrolled. Among 397 children with both test results, 68 (17%) were QFT-positive and 72 (18%) were TST-positive (>= 10 mm). Agreement between the tests was excellent (94%, kappa = 0.79, 95% CI 0.69-0.89). TB disease was diagnosed in 52/397 (13%) participants: 3 definite, 35 probable and 14 possible TB. QFT sensitivity and specificity for TB disease were respectively 38% and 81%. TST sensitivity and specificity were respectively 35% and 84%. CONCLUSION: While TST and QFT had excellent concordance in this population, both tests had much lower sensitivity for TB disease than has been reported for other age groups. Our results suggested equivalent performance of QFT and TST in the diagnosis of TB disease in young children in a high-burden setting.