Use of the QuantiFERON-TB Gold In-Tube® test to monitor treatment efficacy in active pulmonary tuberculosis

SETTING: Cohort study at a tertiary care hospital.OBJECTIVE: To assess the potential use of QuantiFERON-TB Gold In-Tube® (QFT-G) in monitoring clinical response to anti-tuberculosis treatment.DESIGN: We conducted a cohort study of 76 active pulmonary tuberculosis patients with serial testing by QFT-G at baseline and after 2 and 6 months of treatment. At these time points, we compared the performance of QFT-G with sputum culture status of the study subjects.RESULTS: Compared to baseline, 59 (77.6%) cases showed a decline whereas 17 (22.4%) showed persistent or stronger interferon-gamma (IFN-γ) responses at 2 months. Using robust statistical methods, we observed that QFT-G assessment at 2 months independently and significantly predicted the likelihood of remaining sputum culture-positive at the end of the intensive phase of anti-tuberculosis treatment. A higher IFN-γ concentration by 1 international unit (IU)/ml corresponded to a 45% (95%CI 8-97) higher likelihood of failing to convert to a negative culture, whereas a rising or persistent IFN-γ response was associated with a 17.3 (P = 0.007) times higher likelihood of remaining culture-positive at 2 months.CONCLUSIONS: Our results suggest that QFT-G can potentially be used as a tool to monitor the efficacy of anti-tuberculosis treatment.