Performance of a Whole-Blood Interferon-Gamma Release Assay with Mycobacterium RD1-Specific Antigens among HIV-Infected Persons

OBJECTIVE To evaluate the usefulness of one of IGRAs, QuantiFERON-TB Gold (QFT-G), in human immunodeficiency virus- (HIV-) infected patients with various CD4(+) T cell counts. METHODS The QFT-G assay was performed using QFT-G kits among 107 HIV-infected patients including 9 cases with active tuberculosis (TB). RESULTS In HIV-infected patients with CD4(+) > 50/microL, QFT-G positive rate for active TB patients was 5/6 (sensitivity = 83%), and that for those without active disease was 1/69 (specificity = 99%). The frequency of indeterminate QFT-G test was significantly higher in those with CD4(+) less than 50/microL (P < .0001). At the same time there was a proportional relationship between CD4(+) and interferon-gamma response to mitogen (positive control) in QFT-G test (P = .0001). Conclusions. Our data suggested that QFT-G had high sensitivity and specificity in HIV-infected populations with CD4(+) greater than 50/microL. However, QFT-G did not perform well in HIV-positive patients with CD4(+) less than 50/microL.