Role of quantiferon TB gold assays in monitoring the efficacy of antituberculosis therapy

ABSTRACT

The impact of antituberculous treatment on [IFN]-gamma response to mycobacterial tuberculosis antigens have been widely investigated but the results have been controversial. To evaluate the role of Quantiferon TB gold assays as one of the interferon-gamma release assays [IGRAs] for monitoring the efficacy of antituberculosis therapy in patients with active disease. Thirty patients with active pulmonary TB were enrolled in this cross-sectional study where they were subjected to history taking, clinical examination, chest X-ray, direct smear examination of sputum samples for AFB using Ziehl-Neelson stain performed on three visits; up on enrollment, 2 and 6 months later. Lowenstein Jensen medium cultures of sputum samples were done for isolation of Mycobacterium tuberculosison first visit. All patients in the study group were subjected to QuantiFERON-TB Gold estimation on the three visits. The mean sensitivity and specificity of QFT-G test was 85.9% and 62.6% respectively. Using [2] analysis, there was a statistically significant association between QFT-G results and culture results upon enrollment and Acid fast bacilli positivity on second and third visits. Studying the changes in QFT-G results throughout the whole study period revealed a statistically significant decrease in number of QFT-G positive cases from 24/29 patients [82.8%] at first visit to 4/25 patients [16%] at the third visit. All 21/25 patients [84%] who became QFT-G negative at the end of the study had a complete clinical and microbiological recovery of the TB disease. The analysis of QFT-G assay results showed that in the majority of our TB patients there was a correlation between clinical treatment outcome and changes of IFN-gamma response to M. tuberculosis-specific antigens