Abstract
Objective: Evaluate IP-10 detection for latent tuberculosis infection (LTBI) and active tuberculosis (TB) in children, comparing the results with IFN-γ detection.
Material and methods: IFN-γ released was determined by Quantiferon-TB Gold In Tube (QFN). IP-10 was retrospectively detected in supernatants by an in-house ELISA and analyzed using preset cut offs for positive (6.4ng/ml) and indeterminate (3.5ng/ml) IP-10 test result (Ruhwald, Latorre in prep).
Results: 45 pediatric patients were classified in 3 groups. Group 1: 10 children diagnosed with active TB, with a Mycobacterium tuberculosis positive culture or active clinical TB. Group 2: 15 children enrolled during LTBI screening studies, with a positive QFN. Group 3: 20 healthy control children, with a negative QFN. Sensitivities of both IFN-γ and IP-10 assays were 50% (Group 1). Specificity of IP-10 detection was 100% (Group 3). Combining both cytokines the sensitivity improved to 60%, without a compromise of the specificity. Percentage of positive IP-10 responders among children from group 2 was 66.7%. Two children with negative IP-10 assays from this group had QFN positive borderline results. Global concordance between assays was 82% (κ=0.624). IP-10 released after specific antigens stimulation in active TB patients was significantly higher than in healthy controls (p=0.007), this was not seen for IFN-γ (p=0.199).
Conclusions: IFN-γ and IP-10 sensitivity is low, but combination of both cytokines increased sensitivity without a compromise of the specificity. Lowering IP-10 and IFN-γ cut offs could improve the sensitivity in children.
Concordance between both assays is good.
IP-10 could be an alternative marker for LTBI and active TB in children.
- © 2011 ERS
