IP-10 for the diagnosis and treatment monitoring of tuberculosis in children

Purpose: To determine the utility of interferon-gamma-inducible protein 10 (IP-10) for identifying active tuberculosis (TB) and latent TB infection (LTBI) in children in BCG-vaccinated population, establish its diagnostic performance characteristics, and evaluate changes in IP-10 level during anti-TB-chemotherapy. Methods: Concentrations of IP-10 and IFN-γ were measured in QuantiFERON-TB Gold (QFT) supernatants in children with suspected TB or due to a recent TB contact. A total of 225 children were investigated: 33 with active TB, 48 with LTBI, 83 TB contacts, 20 with suspected TB but other final diagnosis, and 41 controls. In 60 children cytokine responses were evaluated on follow-up visit after 2 months of anti-TB-treatment. Results: IP-10 expression was significantly higher in infected children (active TB and LTBI cases) than in uninfected individuals. IP-10 proved effective in identifying TB infection at its optimal cut-off (>1084.5 pg/ml), but was incapable of differentiating between children with active TB and LTBI. Combining IP-10 and IFN-γ increased QFT sensitivity. IP-10 but not IFN-γ decreased significantly during anti-TB-treatment in children with active TB (p = 0.003). Conclusion: IP-10 identifies TB infection and declines during anti-TB-chemotherapy in children. Incorporating IP-10 into new immunodiagnostic assays could improve TB diagnosis and allow treatment monitoring.