Evaluation of QuantiFERON-TB Gold test for the diagnosis of tubercular infection in children

Abstract

BackgroundTuberculin skin test (Mantoux test) is a known intradermal skin prick test for detection of tubercular infection in children and adult population. A new diagnostic test QuantiFERON-TB (QFT) Gold developed in 2005 and approved by the US Food and Drug Administration has good sensitivity and specificity for diagnosis of tubercular infection. MethodsIn this prospective study, 125 children who were being evaluated for tubercular infection or disease were administered Mantoux test and at the same time a blood sample was drawn for the interferon gamma estimation and evaluated by this new diagnostic assay, i.e., QFT Gold assay. ResultsSensitivity and specificity of QFT test calculated was 96.4% and 81% respectively, whereas the negative predictive value and positive predictive value were 91.9% and 90.9% respectively. The sensitivity and specificity of the Mantoux test was found to be 89.2% and 59.5% respectively. The Cohen Kappa coefficient between the Mantoux test and QFT Gold assay for diagnosis of tubercular infection was found to be 0.627 (95% confidence interval: 0.474–0.779; p = 0.0001) in our study, indicating a good agreement between the two tests. ConclusionQFT Gold assay is an effective tool in diagnosing tuberculosis infection in a pediatric population. False positive reactions with tuberculin skin test are common as there is cross-reactivity with non-tubercular mycobacteria (NTM) and BCG vaccination. Both sensitivity and specificity of QFT test were better than those of the tuberculin skin test. Therefore, it is better than the tuberculin skin test, and the diagnostic yield is better. However, this test should not be used as gold standard for diagnosis of tubercular disease in children.