Detection and Prediction of Active Tuberculosis Disease by a Whole-Blood Interferon-γ Release Assay in HIV-1-Infected Individuals

Background. The sensitivity of whole-blood interferon-gamma release assays to detect or predict active tuberculosis in individuals infected with human immunodeficiency virus type 1 (HIV-1) has as yet not been determined. Methods. In this prospective, longitudinal, single-center study, 830 HIV-1-infected patients underwent testing with the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay. Clinical screening for active tuberculosis was performed at least every 3 months for a median follow-up time of 19 months. Results. At baseline, the QFT-GIT assay yielded positive or indeterminate results in 44 (5.3%) and 47 (5.7%) of the 830 patients, respectively. A positive QFT-GIT assay result occurred at significantly higher frequencies among black individuals than among white individuals (odds ratio, 4.84; 95% confidence interval, 2.25-9.97;), P < .001 among patients from Africa than among patients from Austria (odds ratio, 6.57; 95% confidence interval, 2.99-14.25;), and among patients from high-prevalence countries than among patients from low-prevalence P < .001 countries (odds ratio, 5.86; 95% confidence interval, 2.41-13.44;). In patients with indeterminate QFT-GIT assay results, both median actual and nadir CD4(+) T cell counts were significantly lower than in patients with interpretable QFT-GIT assay results (P < .001). At the time of baseline QFT-GIT screening, active tuberculosis was P < .001 found in 7 (15.9%) of 44 individuals with a positive result and in 1 (0.1%) of 739 patients with a negative result. During the follow-up period, however, progression to active tuberculosis occurred exclusively in patients with a positive QFT-GIT assay result, at a rate of 8.1% (3 of 37 patients;). Collectively, the sensitivity of the P < .001 QFT- GIT assay for active tuberculosis was 90.9% (95% confidence interval, 62.3%-98.4%). Conclusions. Our results suggest that the QFT-GIT assay may be a sensitive tool for the detection and prediction of active tuberculosis in HIV-1-infected individuals.