Figure 1: Comparison of two simultaneous IGRAs. Blood samples from 120 HCW were simultaneously examined using two different IGRAs. IFNconcentrations are shown. In both assays, a level of IFN- less than 0.1 IU/ml constituted a negative result. IFN- levels falling in the shaded area (0.1 IU/ ml ≤ IFN- level <0.35 IU/ml) are regarded as intermediate in Japan. An arrow indicates one case that yielded an intermediate QFT-GIT test result, but who was positive by QFT-G, although the IFN-level was just above the (lower) positive cut-off value in the latter test.