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New in vitro test, the Interferon-γ assay, has now emerged for diagnosis of latent tuberculosis infection (LTBI). Newer assays based on the immune response to ESAT-6 and CFP-10 antigens from the RD1 of M. tuberculosis may have advantages over TST, in terms of higher specificity, better correlation with exposure to M. tuberculosis and less cross-reactivity due to BCG vaccination and non-TB mycobacterial infection.Two commercially available tests have been approved for the diagnosis of TB infection, the QuantiFERON® TB-Gold and the T Spot.TB. These assays are based on overlapping peptides of ESAT-6 and CFP-10; however, they do not discriminate between A-TB and LTBI. Differently, using multiepitopic peptides from ESAT-6 and CFP-10 proteins selected by quantitative implemented HLA peptide-binding motifs analysis, it has bee shown a positive response to RD1 selected peptides only in patients with A-TB.Aim of this study is to evaluate the test TB-Gold as a tool to identify TB infection in a population enrolled with suspicious active TB. Agreement between TST and Interferon-γ assay (80%), rather then sensivity and specifity was reported. Moreover the assay based on RD1 selected peptides was used to evaluate whether it would allow a discrimination between active TB and LTBI. Our study suggest, that TB-Gold is useful tool to identify TB infection in a population enrolled with suspicious active TB. Moreover the assay based on RD1 selected peptides is a useful tool to discriminate between active TB and LTBI with a positive predictive value of 100% and a negative predictive value of 76%.
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