A subsequent review by Overton et al. similarly concluded that the rate of reactivity of both IGRAs and TST was affected by the level of HIV-associated CD4 T-cell deficiency and that all assays appeared to be affected by the degree of CD4 T-cell depletion, with the possible exception of the TSPOT.TB assay [19, 20]. This evidence concerns the gene CD4 and congenital T-cell immunodeficiency.