Table 1.

Clinical performances of Novalisa SARS-CoV-2 (COVID-19) IgA, IgM and IgG, obtained using as thresholds the value 11 NovaTec units (NTU) (claimed by manufacture’s inserts COVA940_20200416_EH, COVM0940_20200416_EH and COVG0940_20200416_EH) and the best cut-off defined by Youden index (obtained with the Overall data).

Assay	Threshold	Time-frame	Sensitivity§ (95%CI)	Specificity§ (95%CI)	PLR (95%CI)	NLR (95%CI)
SARS-CoV-2 IgA	11 NTU	<12 d	44.8 (26.4–64.3)	100.0 (91.6–100.0)	38.7 (2.4–626.2)	0.56 (0.40–0.77)
		≥12 d	75.7 (66.3–83.6)		64.9 (4.1–1023.4)	0.25 (0.18–0.35)
		Overall	69.0 (60.3–76.8)		59.2 (3.7–933.7)	0.32 (0.24–0.41)
	6 NTU	<12 d	65.5 (45.7–82.1)	97.6 (87.4–99.9)	27.5 (3.9–194.3)	0.35 (0.21–0.58)
		≥ 12 d	84.5 (76.0–90.9)		35.5 (5.1–246.4)	0.16 (0.10–0.25)
		Overall	80.6 (72.7–87.0)		33.9 (4.9–235.2)	0.20 (0.14–0.28)
SARS-CoV-2 IgM	11 NTU	<12 d	27.6 (12.7–47.2)	97.6 (87.4–99.9)	8.1 (1.53–43.2)	0.74 (0.59–0.94)
		≥12 d	53.4 (43.3–63.3)		15.3 (3.1–74.4)	0.48 (0.39–0.60)
		Overall	48.8 (39.9–57.8)		20.5 (2.9–143.4)	0.52 (0.44–0.62)
	5 NTU	<12 d	48.3 (29.4–67.5)	88.1 (74.4–96.0)	4.1 (1.6–10.0)	0.59 (0.41–0.85)
		≥12 d	79.6 (70.5–86.9)		6.7 (2.9–15.3)	0.23 (0.16–0.34)
		Overall	72.9 (64.3–80.3)		6.1 (2.7–14.0)	0.31 (0.23–0.42)
SARS-CoV-2 IgG	11 NTU	<12 d	44.8 (26.4–64.3)	100.0 (91.6–100.0)	38.7 (2.4–626.2)	0.56 (0.40–0.77)
		≥12 d	90.3 (82.9–95.2)		77.3 (4.9–1217.2)	0.10 (0.06–0.18)
		Overall	79.8 (71.9–86.4)		68.5 (4.4–1078.6)	0.21 (0.15–0.29)
	9 NTU	<12 d	48.3 (29.4–67.5)	97.6 (87.4–99.9)	20.3 (2.8–145.8)	0.53 (0.37–0.76)
		≥12 d	94.2 (87.8–97.8)		39.5 (5.7–274.4)	0.06 (0.03–0.13)
		Overall	83.7 (76.2–89.6)		35.2 (5.1–244.2)	0.17 (0.11–0.25)

PLR = positive likelihood ratio; NLR = negative likelihood ratio; d = days.

Subjects included in the analyses: Overall, n = 171; time frame < 12 d, n = 71 (positive and negative to SARS-CoV-2 rRT-PCT); time frame ≥ d, n = 145 (positive and negative to SARS-CoV-2 rRT-PCR).

^§Sensitivities and specificities values are expressed as percentages.