Clinical evaluation of QuantiFERON TB-2G test in patients with healed pulmonary tuberculosis

We evaluated the response to the QuantiFERON TB-2G (QFT-2G) test in patients with healed pulmonary tuberculosis (TB) compared to the response in those with active pulmonary TB. The subjects were 208 patients with healed pulmonary TB and 155 patients with active pulmonary TB. The QFT-2G test results were analyzed by stratifying them into 5- or 10-year periods after the completion of antituberculosis treatment. Of the 208 patients with healed pulmonary TB, 63% had a positive tuberculin skin test (TST) and 34% had a positive QFT-2G test result. There was no significant difference in the positive response rate for the QFT-2G test, or in the positive test result rate for only the early secretory antigenin target 6-kD protein (ESAT-6) antigen, only the culture filtrate protein 10 (CFP-10) antigen, or both the ESAT-6 and CFP-10 antigens among any subgroups stratified by 5- or 10-year periods after the completion of antituberculosis treatment. The positive rate for the QFT-2G test was significantly higher in patients with active pulmonary TB (83%) than in patients with healed pulmonary TB (34%). Regarding the combined and separate responses to both the ESAT-6 and CFP-10 antigens, the positive response rate for both antigens was significantly lower in patients with healed pulmonary TB than in those with active pulmonary TB. Because many patients continued to show a positive response to the QFT-2G test even when a long period had passed after the completion of the antituberculosis treatment, it is suggested that, in patients with a previous history of TB, particular attention must be paid to the relapse of TB or reinfection with TB.