TABLE 3.

IFN-γ values measured from TB antigen-tube-minus nil tube, TB antigen tube, and nil tube of TBF and QFT-GIT compared to those for TBF tubes/QFT-GIT ELISA and QFT-GIT tubes/TBF ELISA^a

Tube and result	Median (interquartile range) IFN-γ concn (IU/ml)				P value	Kruskal-Wallis groupingb
	TBF	QFT-GIT	TBF tubes/QFT-GIT	QFT tubes/TBF
TB antigen minus nil
Total	0.00 (0.00–0.08)	0.01 (0.00–0.09)	0.00 (0.00–0.03)	0.01 (0.00–0.09)	<0.001	a, a, b, a
Positive	1.02 (0.42–2.24)	1.30 (0.71–4.53)	1.06 (0.56–4.36)	1.20 (0.59–3.31)	0.089
Negative	0.00 (0.00–0.04)	0.00 (0.00–0.04)	0.00 (0.00–0.02)	0.00 (0.00–0.04)	<0.001	a, a, b, a
TB antigen
Total	0.23 (0.17–0.35)	0.13 (0.07–0.31)	0.07 (0.05–0.14)	0.22 (0.16–0.39)	<0.001	a, b, c, a
Positive	1.28 (0.70–2.57)	1.52 (0.86–6.16)	1.15 (0.61–4.45)	1.53 (0.86–2.92)	0.298
Negative	0.22 (0.17–0.29)	0.11 (0.07–0.19)	0.07 (0.04–0.11)	0.20 (0.16–0.30)	<0.001	a, b, c, a
Nil
Total	0.21 (0.17–0.29)	0.09 (0.06–0.14)	0.06 (0.04–0.10)	0.19 (0.15–0.27)	<0.001	a, b, c, a
Positive	0.25 (0.18–0.35)	0.12 (0.06–0.24)	0.07 (0.04–0.13)	0.21 (0.18–0.40)	<0.001	a, b, c, a
Negative	0.21 (0.17–0.27)	0.09 (0.06–0.15)	0.06 (0.04–0.10)	0.19 (0.15–0.26)	<0.001	a, b, c, d

^aAbbreviations: TBF, Standard E TB-Feron ELISA; QFT-GIT, QuantiFERON-TB Gold In-Tube assay; QFT ELISA, QuantiFERON-TB Gold In-Tube ELISA.

^bThe same letter (a) indicates nonsignificant differences between groups based on the Mann-Whitney U test or Scheffe’s multiple-comparison test.