Objective: Until recently, the only tool for detection of latent tuberculosis infection (LTBI) was the tuberculin skin test (TST). QuantiFERON-TB Gold In-Tube test (QFT) is a promising in vitro diagnostic test for LTBI that has potential advantages over the TST. In this study we aimed to compare QFT with TST for diagnosis of LTBI.
Patients and methods: A total of 186 BCG-vaccinated subjects enrolled in study. They underwent TST and QFT assay. They divided in two groups. Group 1 includes individuals who were at low risk for exposure to M. tuberculosis (LRG) and Group 2 includes individuals who were likely to have been exposed to M. tuberculosis infections (HRG).
Results: Overall agreement between QFT and TST was 89.3% (kappa = 0.052). In LRG, agreement between the two tests was 52.6% (95% confidence interval, 44-60%) with kappa-values of 0.019. In HRG agreement between the two tests was 63.2% (95% confidence interval, 42-84%) with kappa-values of 0.28.
Conclusion: In conclusion, the QFT assay showed acceptable results for determining latent M. tuberculosis infection in vaccinated population. The decision to select QFT over TST will depend on the population, purpose of testing and resource availability.