Table 1. Interpretation Criteria used for QuantiFERON-TB Gold and QuantiFERON-TB Gold In-Tube^a Tests.

Interpretation	[Nil]b	TB Responsec d	Mitogen Responsee
Positive	Any	≥0.35 IU/mL and ≥50% of [Nil]	Any
Negative	≤0.7 IU/mL	<0.35 IU/mL	≥0.5 IU/mL
Indeterminate	≤0.7 IU/mL	<0.35 IU/mL	<0.5 IU/mL
	>0.7 IU/mL	<50% of Nilc	Any

^aInterpretation criteria used for QFT-GIT differed from that approved by the FDA in Nov, 2008.

^b“[Nil]” is the IFN-γ concentration in plasma from unstimulated blood.

^c“TB Response” for the QuantiFERON-TB Gold test is the higher IFN-γ concentration in plasma from blood stimulated by a cocktail of peptides representing ESAT-6 or CFP10, minus [Nil].

^d“TB Response” for the QuantiFERON-TB Gold In-Tube test is the IFN-γ concentration in plasma from blood stimulated by a single cocktail of peptides representing ESAT-6, CFP10, and part of TB7.7 minus [Nil].

^e“Mitogen Response” is the IFN-γ concentration in plasma from mitogen stimulated blood minus [Nil].