Progress in interferon-gamma release assay development and applications: an unfolding story of translational research.

The introduction of blood-based tests for M. tuberculosis (Mtb) infection approximately 15 years ago was a turning point for diagnosis of latent tuberculosis (TB). Interferon-gamma release assays (IGRAs), which measure Mtb antigen-specific T cell responses, include the ELISpot-based T-SPOT.TB (Oxford Immunotec, Abingdon, UK) and the ELISA-based QuantiFERON Gold In-Tube (QFT-GIT; Qiagen, Hilden, Germany)