Analysis of an interferon-gamma release assay for monitoring the efficacy of anti-tuberculosis chemotherapy.

The reported effect of anti-tuberculosis chemotherapy on interferon-gamma (IFN-γ) release in response to specific Mycobacterium tuberculosis antigens has been inconsistent. The objective of this study was therefore to determine the effect of anti-tuberculosis chemotherapy on IFN-γ response to ESAT-6 and CFP-10. QuantiFERON®-TB Gold (QFT-G) was performed, and the IFN-γ response to ESAT-6 and CFP-10 were measured, for 50 people with culture-confirmed tuberculosis prior to initiating treatment and periodically for up to 120 weeks following initiation of said treatment. IFN-γ responses and bacteriological response were compared. The average IFN-γ response to ESAT-6 and CFP-10 and the proportion of QFT-G results that were positive decreased during chemotherapy and for several weeks thereafter, reaching lows at weeks 48 to 56. Furthermore, these measures were lower at 48 weeks for those with bacteriological reversion prior to the second monthly visit than for those with slower reversion. Although it was shown that anti-tuberculosis treatment generally reduced the specific release of IFN-γ, the effect is so variable that it could be used as a monitor of progress of chemotherapy with great care and reservation.