Comparison of tuberculin skin test and QuantiFERON-TB Gold In-Tube test in Bacillus Calmette-Guerin-vaccinated children

Objectives The aim of this study is to determine the concordance between QuantiFERON-TB Gold In-Tube (QFT-GIT) and tuberculin skin test (TST) in children vaccinated with Bacillus Calmette-Guerin (BCG). Methods This cross-sectional study was done at a pediatric tertiary care center in 33 BCG-vaccinated children aged 6 months-15 years suspected of Mycobacterium tuberculosis infection or in contact with a patient with open tuberculosis (TB). All patients were tested for TST with purified protein derivative-S 5 tuberculin units and QFT-GIT assays. Concordance was evaluated between TST and QFT assay by kappa coefficient (k). Agreement between the tests was classified into categories: poor if k Results Both the TST and QFT assay were positive in 13 and negative in eight children, respectively, resulting in an agreement of 63% (κ = 0.31). Eight children were 4 years of age, TST specificity was 50% with a positive predictive value of 66.7%. In patients with contact with a patient having TB, TST specificity was 33.3%. Considering TST of 15 mm and above as positive, TST specificity increased to 63.2% and a positive predictive value was 56.3%. Conclusion The concordance of TST and QFT-GIT is low in children with previous BCG vaccination and especially in children <4 years of age. QFT-GIT may help to rule out false-positive TST.