Table 1.

Comparison of RT-PCR and antigen assay results in the selected cohort of 226 nasopharyngeal swabs (A) and in the real-time screening cohort of 1738 swabs (B), according to different cutoff values to discriminate positive and negative samples.

			RT-PCR (35 Ct cutoff)
A	Antigen assay cutoff (ng/mL)		Positive (%)	Negative (%)	Total (%)
Selected cohort	1.340	Positive	86 (38.0)	11 (5.0)	97 (43.0)
		Negative	9 (4.0)	120 (53.0)	129 (57.0)
		Total	95 (42.0)	131 (58.0)	226 (100.0)
	1.240	Positive	88 (38.9)	12 (5.3)	100 (44.2)
		Negative	7 (3.1)	119 (52.7)	126 (55.8)
		Total	95 (42.0)	131 (58.0)	226 (100.0)

			RT-PCR (35 Ct cutoff)
B	Antigen assay cutoff (ng/mL)		Positive (%)	Negative (%)	Total (%)
Screening cohort	1.340	Positive	90 (5.2)	130 (7.5)	220 (12.7)
		Negative	0 (0.0)	1518 (87.3)	1518 (87.3)
		Total	90 (5.2)	1648 (94.8)	1738 (100.0)
	1.645	Positive	90 (5.2)	86 (4.9)	176 (10.1)
		Negative	0 (0.0)	1562 (89.9)	1562 (89.9)
		Total	90 (5.2)	1648 (94.8)	1738 (100.0)