Comparison of two interferon-gamma release assays for pediatric tuberculosis infection
James T Gaensbauer, Randall R Reves, Dolly Katz, Amina Ahmed, Thara Venkatappa,Abstract
Introduction
Identifying tuberculosis infection (TBI) using interferon-gamma release assays (IGRAs) is a primary component of clinical and public health efforts to prevent pediatric tuberculosis. Pediatric data comparing the two IGRAs in the United States are very limited. We compared the performance of the two IGRAs among a large pediatric cohort tested for TBI and assessed whether discordance might be due to quantitative results close to test cut-off values.
Methods
Children aged 0–15 years with both T-SPOT.TB (T-SPOT) and QuantiFERON TB-Gold In-Tube (QFT-GIT) tests were identified from a U.S. multicenter study enrolling people at elevated risk of TBI or progression to TB disease. Results were compared using McNemar’s Chi-square tests with stratification by age category and testing reason. Percent agreement and kappa statistics were also calculated. We characterized quantitative test results among children with discordant QFT-GIT-positive/T-SPOT-negative results.
Results
Among 3,793 children, a higher number had positive QFT-GIT than T-SPOT (10.1% vs 7.4%, p < .001). This difference was noted for all age categories except <2 years, and for children with close-contact and non-close contact test indications. Among discordant QFT-GIT-positive/T-SPOT-negative children, lowering the positive threshold for T-SPOT to include borderline spot counts (5–7) did not eliminate the discordance, nor were QFT-GIT antigen-minus-nil results concentrated in the range just above the standard cut-off of 0.35 IU/mL.
Conclusions
In a large pediatric cohort tested for TBI, QFT-GIT had a higher proportion of positive results than T-SPOT, and discordance was not related to quantitative results close to the established diagnostic cut-offs.