The effect of age on whole blood interferon-gamma release assay response among children investigated for latent tuberculosis infection.
OBJECTIVE
To evaluate the effect of age upon QuantiFERON-TB Gold-In-Tube (QFT-IT) assay outcome among children examined for latent tuberculosis infection (LTBI).


METHODS
A cross-sectional study was conducted among 761 children (mean age ± SD: 7.84 ± 4.68 years) evaluated for LTBI. Participants were examined with both tuberculin skin test and QFT-IT (Cellestis, Australia) and categorized into 4 age groups. Multivariate logistic and linear regressions were used to evaluate the association between selected demographic and patient characteristics upon the qualitative and quantitative QFT-IT outcomes. Agreement between the tuberculin skin test and QFT-IT within groups was evaluated with the κ statistic.


RESULTS
QFT-IT indeterminate results occurred more frequently among young children (8.1%; P < .0001) and children (2.7%; P = .025) than adolescents (0.7%). Among QFT-IT positive patients, infants had higher mean (± SD) interferon-gamma (IFNγ) concentration than adolescents. QFT-IT positive (vs negative) outcome was associated with origin from a high tuberculosis endemicity setting (AOR = 4.54; 95% CI, 3.22-6.25) and lack of previous Bacille Calmette Guerin immunization (AOR = 2.70; 95% CI, 1.89-3.85), but not patient age (AOR = 0.96; 95% CI, 0.92-0.99). However, among QFT-IT positive patients, the IFNγ concentration was inversely associated with patient age (P = .009) and positively with mitogen response (P = .0002). Agreement between tests was not significantly different between younger and older children in the different risk groups.


CONCLUSIONS
Qualitative QFT-IT assay results are not affected by patient age. However, indeterminate results occur more frequently among younger children. Among patients with LTBI the quantitative QFT-IT result (ie, IFNγ) is inversely associated with patient age.
Second University Department of Pediatrics, P. and A. Kyriakou Children's Hospital, National and Kapodistrian University of Athens School of Medicine, Athens, Greece.
Elena
E
Critselis
Virginia
V
Amanatidou
Garyfallia
G
Syridou
Nikos P
NP
Spyridis
Mersini
M
Mavrikou
Nikos G
NG
Papadopoulos
Maria N
MN
Tsolia
D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis*; D016015:Logistic Models; D008297:Male; D015203:Reproducibility of Results