A Three-Way Comparison of Tuberculin Skin Testing, QuantiFERON-TB Gold and T-SPOT. TB in Children

Background: There are limited data comparing the performance of the two commercially available interferon gamma (IFN-gamma) release assays ( IGRAs) for the diagnosis of tuberculosis ( TB) in children. We compared QuantiFERON-TB gold In Tube (QFT-IT), T-SPOT. TB and the tuberculin skin test (TST) in children at risk for latent TB infection or TB disease. Methods and Findings: The results of both IGRAs were compared with diagnosis assigned by TST-based criteria and assessed in relation to TB contact history. Results from the TST and at least one assay were available for 96 of 100 children. Agreement between QFT-IT and T-SPOT. TB was high (93% agreement, kappa = 0.83). QFT-IT and T-SPOT. TB tests were positive in 8 (89%) and 9 (100%) children with suspected active TB disease. There was moderate agreement between TST and either QFT-IT (75%, kappa = 0.50) or T-SPOT. TB ( 75%, kappa = 0.51). Among 38 children with TST-defined latent TB infection, QFT-IT gold and T-SPOT. TB assays were positive in 47% and 39% respectively. Three TST-negative children were positive by at least one IGRA. Children with a TB contact were more likely than children without a TB contact to have a positive IGRA (QFT-IT LR 3.9; T-SPOT. TB LR 3.9) and a positive TST (LR 1.4). Multivariate linear regression analysis showed that the magnitude of both TST induration and IGRA IFN-gamma responses was significantly influenced by TB contact history, but only the TST was influenced by age. Conclusions: Although a high level of agreement between the IGRAs was observed, they are commonly discordant with the TST. The correct interpretation of a negative assay in a child with a positive skin test in clinical practice remains challenging and highlights the need for longitudinal studies to determine the negative predictive value of IGRAs.