Accuracy and agreement of the Tuberculin Skin Test (TST) and the QuantiFERON-TB Gold In-tube test (QFT) in the diagnosis of tuberculosis in Indian children

Purpose: Accurate diagnosis of TB in children is hampered by poor specificity of symptoms in endemic countries and the paucibacillary nature of childhood TB. This study was done to compare the accuracy and agreement of the tuberculin skin test (TST) and the QuantiFERON-TB Gold In-tube test (QFT) in diagnosing tuberculosis (TB) in a predominantly BCG-vaccinated population of children.

Methods: This retrospective cohort study enrolled all children aged 1-15 years who underwent TST and QFT testing as part of screening for TB. Children were classified according to the 2014 WHO case definition of TB, and statistical analysis was done to generate data on concordance between the TST and the QFT as well as sensitivity and specificity within WHO-defined groups.

Results: TST and QFT concordance was 83.9% overall (kappa 0.51), 79% in those with WHO-defined TB and 89% in those without TB. TST+/QFT-discordance was commoner than QFT+/TST- discordance across groups. The sensitivity of the TST vs. the QFT was 70.8% vs. 50% for WHO-defined TB, with comparable specificity at 89% vs. 90% respectively.

Conclusions: The higher sensitivity of the cheaper and simpler TST supports its use for TB diagnosis in a normally nourished population of BCG-vaccinated children.