Performance of a New Generation IGRA in Immunocompromised Individuals

This study is designed to evaluate the performance of a new ELISA based QuantiFERON-TB plus In-tube test to identify M. tuberculosis specific immune Responses as evidence of latent infection with M. tuberculosis in immunosuppressed populations. Both qualitative and quantitative test results will be related to the level of immunodeficiency and to the presence of risk factors for prior exposure with M. tuberculosis. In addition, patients with active tuberculosis (both immunocompetent and immunocompromised individuals) will be included to evaluate a potential increase in sensitivity in these groups. Immunocompetent individuals with low risk of exposure will be analysed as a proxy to estimate specificity. Finally, this study will be extended to longitudinally assess the predictive value of a positive blood test for progression to active disease.