ABSTRACT
SETTING: Interferon-gamma (IFN-γ) release assays (IGRAs) play an important role in the diagnosis of Mycobacterium tuberculosis infection. However, in children with tuberculosis (TB), some studies have shown increased frequencies of false-negative or indeterminate IGRA results. OBJECTIVE: To analyse the spectrum of different cytokines to improve the diagnostic accuracy of IGRAs in latent tuberculous infection (LTBI) and active TB. DESIGN: We performed multiplex cytokine expression analysis of QuantiFERON® Gold In-Tube supernatants in children with active TB (n = 21) and disease-free contacts with (n = 15) and without LTBI (n = 12), to determine the sensitivity and specificity of the modified tests. RESULTS: Of 21 initial cytokines analysed, IFN-γ and six other candidates (interleukin [IL] 2, inducible protein 10 [IP-10], IL-13, IL-1α, tumour necrosis factor alpha [TNF-α] and granulocyte-macrophage colony-stimulating factor [GM-CSF]) were significantly more elevated in children with TB and those with LTBI than in the non-infected controls. Sensitivity and specificity were similar for IFN-γ and IL-2, but lower for the remaining candidates. Notably, a subset of candidates, including IP-10, showed M. tuberculosis antigen-induced specific expression in non-infected children. None of the candidates showed differences in expression between children with TB and those with LTBI. CONCLUSIONS: Our results did not suggest that alternative IGRA cytokines can distinguish between children with active TB and those with LTBI. IFN-γ and IL-2 showed comparable capacity in diagnosing M. tuberculosis infection in our study groups.
