Analysis of QuantiFERON-TB gold plus assay in children and young adults with Mycobacterium tuberculosis infection in China

Abstract Objective We aimed to evaluate the diagnostic performance of QuantiFERON-TB Gold Plus (QFT-Plus) assay in children and young adults with active tuberculosis (TB) and latent tuberculosis infection (LTBI) in China. Methods Patients aged<22 years with confirmed Mycobacterium tuberculosis (MTB) infection who additionally had QFT-Plus results and complete clinical information were enrolled retrospectively at Beijing Children’s Hospital and Shenyang Chest Hospital from August 2022 to March 2024. The productions of interferon gamma (IFN-γ) in response to TB-specific antigens were also analyzed. Results A total of 448 patients were enrolled, comprising 138 (30.8%) individuals with active TB disease and 310 (69.2%) with LTBI. The overall sensitivity for active TB was 82.8%. The percent agreement between TB1 and TB2 was 91.8%. The IFN-γ production in response to mitogen and TB antigens observed among children <1 year of age was lower than that among other age groups. There was significant positive correlation between age and IFN-γ responses to mitogen, but negative correlation between age and IFN-γ responses to TB1 and TB2 antigen. Besides, there was no significant difference in response to QFT-Plus TB antigens in active TB and LTBI cases. Conclusion This study shows that QFT-Plus provides a useful diagnostic aid in diagnosis of active TB and LTBI in children and young adults. A suboptimal sensitivity and higher indeterminate rate was observed in children younger than 1 year old and those with comorbidities, precluding their use as a rule-out test.