Sensitivity and specificity of QuantiFERON-TB Gold Plus compared with QuantiFERON-TB Gold In-Tube and T-SPOT.TB on active tuberculosis in Japan.

Background: The QuantiFERON-TB Gold Plus (QFT-Plus) was introduced in 2015 as a new generation of interferon-gamma release assays (IGRAs) designed to detect Mycobacterium tuberculosis infection (TB). Examination of its diagnostic accuracy is crucial before it is launched in Japan.

Method: We examined 99 patients with laboratory-confirmed active TB (patients) and 117 healthy volunteers with no risk of TB infection (controls) at a medical center in Tokyo, Japan. Blood samples were collected from both the patients and controls and tested using three types of IGRAs: the QFT-Plus, the QuantiFERON-TB Gold In-Tube (QFT-GIT), and the T-SPOT.TB (T-SPOT). The sensitivity and specificity of each IGRA were examined and compared.

Results: The sensitivity of the QFT-Plus was 98.9% (95% confidence interval [CI], 0.934-0.998) and similar to that of the QFT-GIT (97.9%; 95% CI, 0.929-0.998) and T-SPOT (96.9%; 95% CI, 0.914-0.994). The specificity of the QFT-Plus was the same as that of the QFT-GIT and T-SPOT (98.1%; 95% CI, 0.934-0.998). One patient with uncontrolled diabetes mellitus showed negative results on all three IGRAs.

Conclusions: The QFT-Plus showed a high degree of agreement with the QFT-GIT and T-SPOT, with high sensitivity and specificity. Severe diabetes mellitus may influence the results of IGRAs. Larger studies are needed to validate the accuracy of the GFT-Plus and determine whether it can contribute as adjunctive method for the early diagnosis of active TB in Japan.