title: Usefulness of interferon-γ release assay for the diagnosis of latent tuberculosis infection in young children.
abstract: OBJECTIVE
  Latent tuberculosis infection (LTBI) in young children may progress to severe active tuberculosis (TB) disease and serve as a reservoir for future transmission of TB disease. There are limited data on interferon-γ release assay (IGRA) performance in young children, which our research aims to address by investigating the usefulness of IGRA for the diagnosis of LTBI.
  
  
  METHODS
  We performed a tuberculin skin test (TST) and IGRA on children who were younger than 18 years and were admitted to Chung-Ang University Hospital during May 2011-June 2015. Blood samples for IGRA were collected, processed, and interpreted according to manufacturer protocol.
  
  
  RESULTS
  Among 149 children, 31 (20.8%) and 10 (6.7%) were diagnosed with LTBI and active pulmonary TB, respectively. In subjects lacking contact history with active TB patients, TST and IGRA results were positive in 41.4% (29 of 70) and 12.9% (9 of 70) subjects, respectively. The agreement (kappa) of TST and IGRA was 0.123. The control group, consisting of non-TB-infected subjects, showed no correlation between age and changes in interferon-γ concentration after nil antigen, TB-specific antigen, or mitogen stimulation in IGRAs (P=0.384, P=0.176, and P=0.077, respectively). In serial IGRAs, interferon-γ response to TB antigen increased in IGRA-positive LTBI subjects, but did not change considerably in initially IGRA-negative LTBI or control subjects.
  
  
  CONCLUSIONS
  The lack of decrease in interferon-γ response in young children indicates that IGRA could be considered for this age group. Serial IGRA tests might accurately diagnose LTBI in children lacking contact history with active TB patients.
authors.affiliation: Department of Pediatrics, Seoul National University College of Medicine, Seoul, Korea.; Department of Pediatrics, Chung-Ang University College of Medicine, Seoul, Korea.
authors.forename: Ki Wook
authors.initials: KW
authors.lastname: Yun
authors.affiliation: Department of Pediatrics, Chung-Ang University College of Medicine, Seoul, Korea.
authors.forename: Young Kwang
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Chung-Ang University College of Medicine, Seoul, Korea.
authors.forename: Hae Ryun
authors.initials: HR
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Chung-Ang University College of Medicine, Seoul, Korea.
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Lee
authors.affiliation: Department of Pediatrics, Chung-Ang University College of Medicine, Seoul, Korea.
authors.forename: In Seok
authors.initials: IS
authors.lastname: Lim
keywords: Child; Interferon-gamma release assay; Latent tuberculosis infection; Tuberculin skin test