Table 3. Correlations between ODs/OD ratios and PRNT results of 10 serum samples obtained from 3 PCR-confirmed COVID-19 patients from France and tested in Rotterdam, the Netherlands, 6–27 d after diagnosis*.

Test, virus	Correlations	In-house ELISAs						Euroimmun ELISAs
		S1	N	RBD	S	S1A		IgA	IgG
PRNT50, SARS-CoV-2	Spearman ρ value	0.87	0.94	0.92	0.94	0.93		0.98	0.92
	2-tailed p value	0.0021	0.0002	0.0005	0.0002	0.0003		<0.0001	0.0005
	p value summary	<0.01	<0.001	<0.001	<0.001	<0.001		<0.0001	<0.001
PRNT90, SARS-CoV-2	Spearman ρ value	0.88	0.88	0.88	0.88	0.88		0.93	0.88
	2-tailed p value	0.0024	0.0024	0.0024	0.0024	0.0024		0.0008	0.002
	p value summary	<0.01	<0.01	<0.01	<0.01	<0.01		<0.001	<0.01

*COVID-19, coronavirus disease 2019; OD, optical density; N, nucleocapsid; PRNT₅₀, 50% plaque reduction neutralization test; PRNT₉₀, 90% plaque reduction neutralization test; RBD, receptor-binding domain; S, spike; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.