In a retrospective study in Sweden [4], which included TB contacts among others, repeating positive QFT-GIT tests (initial IFN-γ concentration, 0.35–0.99 IU·mL-1) after 3–12 weeks yielded a reversion rate of 54.7%, and reached 59.4% in a subgroup when it was retested within 4 weeks. Here, IFNG is linked to tuberculosis.