Furthermore, Nicol et al. in 2005, reported the specificity between the PPD and the ELISPOT, they found that ESAT-6- or CFP10-specific IFN-γ-producing lymphocytes were detectable at diagnosis in two thirds of children presenting with a clinical diagnosis of tuberculosis; however, responses were more frequently positive in patients with culture-proven disease. Here, IFNG is linked to tuberculosis.