Comparison of specificities between two interferon-gamma release assays in Japan.

We compared the specificities of two interferon-gamma release assays (IGRAs), T-SPOT®.TB (T-SPOT) and the QuantiFERON®-TB Gold In-Tube (QFT-GIT) assay, in strictly selected subjects with a low risk of tuberculosis (TB) infection in a Japanese population. Of 111 subjects who were mostly bacille Calmette-Guérin vaccinated, one was positive using both assays and 110 were negative, using international cut-off values. Although several meta-analyses report that QFT-GIT has higher specificity than T-SPOT, our study demonstrates that the specificity of both assays is equally high in a population with a truly low risk of TB infection.