Discordance between TSTs and IFN- release assays: the role of NTM and the relevance of mycobacterial sensitins

From the authors: We do appreciate the comments by M. Tebruegge and co-workers about our recently published manuscript in the European Respiratory Journal 1. The aim of this reply is to clarify some points in order to interpret better the results of the study, given that we think there were some misunderstandings. In vitro assays for measuring interferon (IFN)-γ released by the T-cells after specific Mycobacterium tuberculosis stimulation have demonstrated promising results in adults and also in children for diagnosing tuberculosis (TB) infection 2, 3. However, there are discordant results between IFN-γ based assays and the tuberculin skin test (TST) that require clarification in order to assess the real utility of the in vitro tests in the management of patients 2, 4. In our study we determined the potential role of non-tuberculous mycobacteria (NTM) sensitisation in children as a factor of discordant results between TST and an in vitro T-cell based assay (T.SPOT. TB ; Oxford Immunotec, Oxford, UK). We enrolled 21 non-bacille Calmette–Guerin vaccinated paediatric …