[Interferon-gamma assays -- description and assessment of a new tool in the diagnosis of tuberculosis]

Abstract

Up to now the diagnosis of latent tuberculosis infection (LTBI) was based solely on the tuberculin skin test. However, this method offers neither 100 % sensitivity nor -- and this is in particular due to its cross-reactivity with BCG and environmental mycobacteria -- a 100 % specificity. The demand in Germany for a more reliable in vitro test is currently enhanced by the change from the multipuncture test to the intradermal (Mendel-Mantoux) test and by the uncertainty resulting from the ceased production of the tuberculin previously used in Germany. The manufacturers of immunologic test methods such as the QuantiFERON-TB Gold In-Tube (ELISA assay) and the T SPOT-TB Test (ELISPOT assay), which are based on the Interferon-gamma (IFN-gamma) production of sensitized T lymphocytes, offer their products as possible alternatives. This article explains the function of the IFN-gamma tests and gives an overview of the most recent data, possible indications and the open scientific questions to be investigated by future clinical studies. Although the new test methods have the potential to eventually prevail as an additional helpful diagnostic tool, the authors consider a complete replacement of the tuberculin skin test as premature. The IFN-gamma tests may, however, prove already now to be a useful additional diagnostic method.