QuantiFERON TB-2G test for patients with active tuberculosis stratified by age groups

We evaluated the usefulness of the QuantiFERON TB-2G (QFT-2G) test and the tuberculin skin test (TST) in patients with active tuberculosis (TB) disease stratified by age in 10-year increments. Although the positive rate on TST was over 80% in younger patients aged <= 9 years, it decreased to 55% in patients of aged 70-79 years and 33% in patients aged over 80 years. However, the positive rate on QFT-2G test was over 80% for the age groups between 10-19 and 60-69 years, excluding younger patients aged <= 9 years. Furthermore, the rate was 79% in patients aged 70-79 years and 75% in patients over 80 years of age. The positive response rate of the QFT-2G test was significantly higher than that of the TST in patients over 50 years of age. The indeterminate result of the QFT-2G test increased with age and it is suggested that this result is concerned with the severity of underlying diseases in patients with active TB disease. Although the positive rate on QFT-2G test decreased with age in adults, it is thought to be a useful supportive diagnostic method for active TB disease compared to the TST, except in younger patients aged <= 9 years old.