Abstract
Evidence that quantitative T-cell interferon-gamma responses to M. tuberculosis-specific antigens may reflect mycobacterial burden has raised interest in these responses as biomarkers for treatment outcomes.
A cohort of 263 HIV-negative, culture-positive pulmonary TB patients enrolled between August 2005 and May 2007 who completed treatment and who were tested with QuantiFERON-Gold In-tube® (QFT-IT) and T-SPOT.TB® assays pre- and post-treatment were matched with the national TB registry for any re-notification as at December 31 2010.
Four patients relapsed with culture-positive, pansensitive pulmonary TB (relapse rate 1.5%). The time to relapse was 11, 17, 35 and 44 months. All were male. At the time of the first TB episode, their mean age was 45.4 years old, two were diabetic, two were cigarette smokers; all were baseline sputum AFB smear-positive; two had cavitary disease. All received directly-observed, 6-month chemotherapy with four first-line drugs in the intensive phase, followed by thrice weekly Rifampicin and Isoniazid in the continuation phase. All had one negative sputum culture (done once only) at two months of treatment.
All four patients were IGRA positive at baseline. The QFT-IT was negative at end of treatment and 6 months post treatment-completion in three and four patients respectively. All remained T-SPOT positive at treatment completion, while two reverted their T-SPOT results 6 months thereafter. Compared to the whole treatment cohort, a lower proportion of relapsed patients tested IGRA positive at 6 months post-treatment completion (0% vs 46.3% for QFT-IT; 50% vs 79.2% for T-SPOT).
Our observations suggest that the kinetics of interferon-gamma responses are not useful for predicting disease relapse.
- © 2011 ERS