Interferon-gamma release assays and the diagnosis of tuberculosis: have they found their place?

Tuberculosis (TB) remains an important issue in Australia with more than 85% of active cases contributed by overseas-born persons. Other risk groups include older Australians who acquired TB in the past and indigenous people. Immune suppression is an emerging risk factor for TB, particularly due to the expanding group of conditions for which potent immunosuppressive therapies is now used. Screening for latent TB is recommended in many risk groups including recent contacts of those with transmissible TB, those undergoing immune suppressive therapy, recently arrived refugees or migrants from high-risk countries and indigenous people with high rates of TB in the local community. Interferon-gamma release assay (IGRA) has now been available for several years for the diagnosis of latent TB. It is now used in many clinical situations, and despite the rapid rate of new publications, there are still gaps in our knowledge. This paper reviews the current role of interferon-gamma release assay in various situations, to determine its place in current practice and to explore where uncertainties exist.