Utility of interferon-γ release assay results to monitor anti-tubercular treatment in adults and children.

BACKGROUND Interferon-γ release assays (IGRAs), including the commercially available T-SPOT.TB, QuantiFERON-TB Gold (QFT-G), and QuantiFERON-TB Gold In-Tube (QTF-G-IT), enable detection of circulating T lymphocytes responsive to specific Mycobacterium tuberculosis antigens. Studies of the potential role of serial IGRAs for assessment of response to anti-tubercular therapy are accumulating. OBJECTIVE The objective of this systematic review was to evaluate the potential clinical utility of serial IGRAs in anti-tubercular therapy. METHODS We conducted a literature search of the Cochrane Library and MEDLINE by PubMed, from database inception through October 1, 2011, for serial IGRA results in anti-tubercular therapy, in adults and children, using commercial stardardized assays. All types of articles in the English language were included. Meta-analysis was performed to estimate the pooled percentage of reversion from a positive to a negative IGRA value at 3- to 6-month follow-up. RESULTS According to inclusion and exclusion criteria, three T-SPOT.TB-based (n = 319 patients), three QFT-G-based (n = 75 patients), and seven QFT-G-IT-based (n = 558 patients) longitudinal studies were included. The percentage of patients with reversion from a positive to a negative IGRA value ranged from 5.71% to 13.93% for T-SPOT.TB, 5.26% to 71.05% for QFT-G, and 14.28% to 41.89% for QFT-G-IT assays. Meta-analysis estimation of reversion was feasible only for the QFT-G-IT assay, at 30.54% (95% CI, 22.89-38.75). In two pediatric studies, which were QFT-G-IT based (n = 122 children), the reported reversion rates were 14.28% and 20.33%, respectively. CONCLUSIONS Because IGRAs require time and cost resources, and reversion from positive to negative IGRA values occurs in a minority of treated patients, monitoring IGRA changes over time seems to have only speculative value in adults. Data in children are poor, but are in line with results reported in adults.