Among 852 samples sent for QuantiFERON®-TB Gold Plus Assay (QFN) analysis, between 6-11% had IFNγ binding activity, but only 1.2% of indeterminate samples had IFNγ blocking activity. No TB negative samples had blocking activity to IFNγ. Indeterminate QFN results may indicate the presence of blocking anti-IFNγ autoantibodies.
Lee et al. (2025) studied this question.