Analysis of QuantiFERON-TB Gold Plus assay in Children and Adolescents with Latent and Active Tuberculosis in China

Objective To evaluate the accuracy of QuantiFERON-TB Gold Plus (QFT-Plus) assay, and analyze the quantitative interferon gamma (IFN-γ) responses to tuberculosis (TB) antigens and mitogen in children and adolescents with active TB and latent tuberculosis infection (LTBI) in China. Methods A retrospective study was conducted among patients <25 years old with suspected active TB or screened for LTBI. All patients underwent QFT-Plus tests at Beijing Children’s Hospital and Shenyang Chest Hospital from August 2022 to March 2024. Demographic and clinical data were extracted from their electronic medical record. Results A total of 18482 patients were recruited, including 179 (1.0%) patients with active TB disease, 334 (1.8%) LTBI and 17969 (97.2%) non-TB disease. The 5.8% (176/18482) patients had indeterminate results. The overall sensitivity for active TB was 83.4%, and specificity was 98.0%. The percent agreement between TB1 and TB2 was 90.3%. 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 QFT-Plus assay is accurate in children and adolescents with active TB. IFN-γ responses to mitogen and MTB antigens are significantly affected by age. The new antigen tube TB2 increases the assay sensitivity.