Clinical evaluation for diagnosing active TB disease and transitional change of two commercial blood tests

We compared the usefulness of TST, QFT-TB and T-SPOT.TB for the identification of patients with active tuberculosis (TB) disease and investigated transitional change in both tests during anti-tuberculous treatment. The subjects were 50 healthy volunteers and 48 patients with active TB disease between October 2005 and December 2006. Among active TB disease patients, 60% had a positive TST result, 81% had a positive QFT-TB result, and 87% had a positive T-SPOT.TB result. Indeterminate results of QFT-TB and T-SPOT.TB were recognized in 12% and 6% of patients, respectively. Negative results on QFT-TB and T-SPOT.TB were 6% each. QFT-TB had a sensitivity of 81% for active TB disease. T-SPOT.TB had a sensitivity of 88% for active TB disease. With regard to transitional changes in QFT-TB results and T-SPOT.TB results, both test results showed a positive response in over 40% of patients 12 months after anti-tuberculous treatment. In conclusion, both blood assays seemed to be more useful than TST for the identification of patients with active TB disease. However, neither of the 2 blood tests appears to provide any certainty regarding the cure of infection.