For reasons related to cost and availability, this tool is the first choice for latent TB diagnosis in our population A negative TST does not rule out latent TB at any age and especially not in immunocompromised host; for this when the risks of infection, of progression to disease and of a poor outcome are high, interferon gamma release tests (IGRAs) may be used as a supplementary diagnostic to enhance the overall sensitivity. Here, IFNG is linked to infection.