First independent evaluation of QuantiFERON-TB Plus performance

TABLE 1

QuantiFERON-TB Plus (QFT-Plus) performance characteristics in different study groups

	Frequency	QFT-Plus result			Positive results in each tube		IFN-γ concentration^¶ IU·mL⁻¹		TB2−TB1 IU·mL⁻¹
	Frequency	Indeterminate	Negative^#	Positive^#	TB1	TB2	TB1	TB2	TB2−TB1 IU·mL⁻¹
Low-risk controls	106	0	103 (97.17)	3 (2.83)	2	1	0.1 (0.09–0.13)	0.11 (0.09–0.13)	0 (−0.01–0.01)
Active TB	119	3	14 (12.07)	102 (87.93)	96	101	2.09 (0.83–6.52)	2.88 (1–7.89)	0.14 (−0.13–0.79)
Sex
Male	72	1	7 (9.86)	64 (90.14)	59	64	2.08 (0.86–6.38)	2.91 (1.17–7.62)	0.23 (−0.14–0.88)
Female	47	2	7 (15.56)	38 (84.44)	37	37	2.09 (0.71–7.03)	2.85 (0.88–7.80)	0.11 (−0.11–0.50)
Smear
Negative	65	1	12 (18.75)	52 (81.25)	51	52	2.12 (0.89–9.51)	2.69 (1.01–9.66)	0.05 (−0.17–0.55)
Positive	54	2	2 (3.85)	50 (96.15)	45	49	2 (0.67–6.04)	3.26 (0.92–6.31)	0.29 (0–1.16)
Localisation
PTB	79	3	9 (11.84)	67 (88.16)	62	66	1.93 (0.57–6.04)	2.82 (0.75–6.22)	0.26 (−0.12–0.80)
EPTB	40	0	5 (12.5)	35 (87.5)	34	35	2.29 (1.23–10)	2.95 (1.15–10)	0.06 (−0.17–0.46)
BCG
Negative	6	0	2 (33.33)	4 (66.67)	4	4	1.15 (0.33–1.86)	1.47 (0.4–2.75)	0.07 (0.01–0.44)
Positive	54	0	4 (7.41)	50 (92.59)	44	50	2.01 (0.9–6.57)	2.79 (1.02–8.2)	0.14 (−0.20–0.65)

Data are presented as n, n (%) or median (interquartile range). IFN: interferon; TB: tuberculosis; PTB: pulmonary tuberculosis; EPTB: extrapulmonary tuberculosis; BCG: bacille Calmette–Guérin. ^#: percentages are based on the total number of valid tests, excluding indeterminate results.