The results were reported as indeterminate if the IFN-γ level of Nil was ≤ 8.0 IU/mL, that of TB antigen minus Nil was< 0.35 IU/mL or ≥ 0.35 IU/mL and < 25% of Nil value, and Mitogen minus Nil was < 0.5 IU/mL (positive control failure) or if the IFN-γ level of Nil was > 8.0 IU/mL (negative control failure). The gene discussed is IFNG; the disease is tuberculosis.