Table 4. Correlations between ODs/OD ratios and PRNT results of 31 serum samples from 9 PCR-confirmed COVID-19 patients tested from Germany and tested in in Berlin, Germany, 3–23 d after disease onset*.

Test, virus	Correlation	Euroimmun ELISAs
		IgA	IgG
PRNT50, SARS-CoV-2	Spearman ρ value	0.63	0.5077
	2-tailed p value	0.056	0.1368
	p value summary	NS	NS
PRNT90, SARS-CoV-2	Spearman ρ value	0.7922	0.8525
	2-tailed p value	0.0004	<0.0001
	p value summary	<0.001	<0.0001

*COVID-19, coronavirus disease 2019; NS, not significant; OD, optical density; PRNT₅₀, 50% plaque reduction neutralization test; PRNT₉₀, 90% plaque reduction neutralization test; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.