Evaluation of treatment response in active tuberculosis using QuantiFERON-TB Gold Plus

Introduction Tuberculosis (TB) is one of the leading infectious causes of death worldwide and despite the progress recently made in TB control at a global level, the decline in its incidence is still slow. It is therefore crucial to evaluate the performance of new tools for monitoring of TB treatment. The aim of this study was to evaluate the response to tuberculosis treatment using the QuantiFERON-TB Gold Plus (QFT-Plus) kit. Methods Blood samples of 100 patients with active TB were taken before treatment and after three months, if treatment was successful and sputum culture was negative. Whole blood was incubated in the presence or absence of the TB antigens, TB1 and TB2-specific antigens, and the production of IFN-gamma was determined using the QuantiFERON-TB Gold Plus (QFT-Plus) test. The data were analyzed using SPSS 16 software and statistical significance was assessed at a two-tailed P value of 0.05. Results The median values of IFN-gamma released following stimulation with TB1 peptides decreased slightly after treatment (2.5 IU/mL (IQR: 0.9-5.3), compared to the baseline (3.4 IU/mL (IQR: 0.5-6.6)). Also, with respect to the TB1 antigen, 38 out of 45 patients were positive for the QFT test before treatment (84.4%) and 37 cases after treatment (82.2%). On the other hand, the median values of IFN-gamma determined with the TB2 test declined marginally after treatment (2.7 IU/mL; IQR: 0.95-5.8), as compared to pretreatment (3.0 IU/ml; IQR: 0.7-8.9). Thirty-nine out of 45 patients (86.7%) before initiation of treatment and 37 cases following a 3-month treatment (82.2%) were had positive values. Moreover, the median values of IFN-gamma of TB2 minus TB1 before and after treatment were 0.17 (IQR: 0-1.0) and 0.03 (IQR: 0.0.48), respectively; however, these differences were not significant (p value=0.29). Conclusion The results of this study show no significant differences between the IFN-gamma release in TB patients prior to and after treatment. However, more extensive studies are needed in different populations with higher sample sizes to validate these results.