[Role of in vitro tests in the diagnosis of latent tubercular infections].

Recent advancements in the understanding of pathogenetic mechanisms in tuberculosis infection, allowed the identification of target molecules and antigens, playing a crucial role in an effective M. tuberculosis immune control. Thanks to this new information, the diagnostic approach to latent tuberculosis infection may be complemented today with two new blood assays, based on the detection and the quantification of the key cytokine interferon-gamma by peripheral blood T cells stimulated with M. tuberculosis-specific antigens. These new tests, QuantiFERON-TB Gold and T-SPOT.TB, being certainly more specific than the tuberculin skin test and probably more sensitive in some subgroups of patients, might represent a crucially relevant tool to achieve to goal of global tuberculosis control. Both assays have logistic advantages over the skin test, thus making them ideal candidates in situations where the tests need to be repeated over time (like in the setting of occupational medicine). In particular, the limited occurrence of the so-called "boosting" effect, the fact that there is no need for a return visit, the reduced variability in reading and reporting of the results and the quantitative response obtained with these assays are all elements that, altogether with the high specificity in BCG-vaccinated individuals, should favor the inclusion of these assays in the process of evaluation of the biologic risk for health care workers. Nonetheless, since these tests have been recently introduced in clinical practice, there are several aspects that still need to be clarified, such as the meaning of the quantitative responses and the interpretation of indeterminate results. It's therefore desirable that new documents will be produced soon to guide the use of these new tests in clinical routine.