TABLE 3.

Specificity of SARS-CoV-2 IgG ELISAs^a

Panel	No. of samples	No. (%) of betacoronavirus IgG-positive samples	A450-A620 cutoff	No. of negative samples, % specificity (95% CI), for ELISA 1 (sera, 1:100)	No. of negative samples, % specificity (95% CI), for ELISA 2 (sera, 1:2)	No. of negative/bl samples, % specificity (95% CI), for Euroimmun NCP IgG
Germany	139	51 (36.7)	0.200	139, 100.0 (96.8–100.0)	139, 100.0 (96.8–100.0)	139, 100.0 (96.8–100.0)
			0.400	139, 100.0 (96.8–100.0)	139, 100.0 (96.8–100.0)
Ghana A	131	33 (25.2)	0.200	128, 97.7 (93.2–99.5)	129, 98.5 (94.3–99.9)	97, 74.0 (65.9–80.8)
			0.400	129, 98.5 (94.3–99.9)	131, 100.0 (96.6–100.0)
Ghana B	145	34 (23.4)	0.200	142, 97.9 (93.8–99.6)	145, 100.0 (96.9–100.0)	132, 91.0 (85.1–94.8)
			0.400	145, 100.0 (96.9–100.0)	145, 100.0 (96.9–100.0)
Madagascar	166	30 (18.1)	0.200	165, 99.4 (96.3–100.0)	166, 100.0 (97.3–100.0)	164, 98.8 (95.4–100.0)
			0.400	166, 100.0 (97.3–100.0)	166, 100.0 (97.3–100.0)
Nigeria	149	79 (53.0)	0.200	143, 96.0 (91.3–98.3)	149, 100.0 (97.0–100.0)	107, 71.8 (64.1–78.4)
			0.400	146, 98.0 (94.0–99.6)	149, 100.0 (97.0–100.0)
Colombia	40	12 (30.0)	0.200	40, 100.0 (89.6–100.0)	40, 100.0 (89.6–100.0)	40, 100.0 (89.6–100.0)
			0.400	40, 100.0 (89.6–100.0)	40, 100.0 (89.6–100.0)
Lao PDR	20	5 (25.0)	0.200	20, 100.0 (81.0–100.0)	20, 100.0 (81.0–100.0)	20, 100.0 (81.0–100.0)
			0.400	20, 100.0 (81.0–100.0)	20, 100.0 (81.0–100.0)

^aSerum/plasma samples collected from symptom-free donors before 2019 in Europe, Africa, South America, and Asia were analyzed with SARS-CoV-2 IgG FcγR ELISAs 1 and 2 and the Euroimmun anti-SARS-CoV-2 NCP ELISA (IgG). Specificities and 95% confidence intervals (CIs) were calculated for two alternative cutoff values (A₄₅₀-A₆₂₀ = 0.2 and 0.4). bl, borderline.