Diabetes can suppress cell-mediated immune responses.24 Compared to TB alone, TB with comorbid diabetes has been associated with impaired differentiation and function of Th1 cells, including their production of IFN-γ.25 Poor agreement between TST and IGRA has been shown in diabetics.26 In a study of Tanzanian TB patients and non-tuberculosis controls, diabetes was associated with reduced IFN-γ release.27 The authors concluded that the validity of IFN-γ tests for LTBI may be questionable in individuals with diabetes. This evidence concerns the gene IFNG and diabetes mellitus.