Dynamic changes of interferon-gamma Release Assay results along with latent tuberculosis infection treatment

Abstract Objectives Using QuantiFERON-TB Gold In-Tube (QFT-GIT) for monitoring tuberculosis (TB) and latent TB infection (LTBI) treatment effect is controversial. The present study aims to evaluate the dynamic changes of interferon gamma (IFN-γ) levels along with LTBI treatment based on a randomized controlled study. Methods 910 participants treated with 8 weeks of once-weekly rifapentine (RPT) plus isoniazid (INH), 890 treated with 6 weeks of twice-weekly RPT plus INH, and 818 untreated controls were followed for 2 years to track active TB development. QFT-GIT tests were repeated three times for all of them: before treatment (T0), upon completion of treatment (T1), and 3 months after completion of treatment (T2). Results Similar rates of persistent QFT-GIT reversion were observed in Group A (19.0%, 173/910), Group B (18.5%, 165/890) and Group C (20.7%, 169/818) (p = 0.512). The dynamic changes of IFN-γ levels were non-significant among the three groups as well. In treated participants, individuals with higher baseline IFN-γ levels showed increased TB occurrence (1.0%, 9/896) as compared to those with lower baseline levels (0.2%, 2/904) (p = 0.037). A similar but non-significant trend was also observed in untreated controls (1.8% (7/400) vs. 0.5% (2/418), p = 0.100). When TB cases were matched with non-TB cases on baseline IFN-γ levels, still no significant differences were found with respect to the dynamic changes in IFN-γ levels with time regardless if treated or not. Conclusions Our results suggested that QFT-GIT reversion or decreased IFN-γ levels should not be used for monitoring host response to LTBI treatment.