Table 1.

Comparative table of the results obtained from the diagnostic test of N4S11-SC2 protein for COVID-19 based on the search for specific IgG antibodies in urine and serum. Samples from symptomatic patients for COVID-19 and with PCR + for SARS-CoV-2, as well as from negative control subjects were used. The individual index (I) value obtained by the Abs/cut-off ratio was used to construct ROC curves. The diagnostic performance of the antigen in relation to the type of sample used was based on the evaluation of sensitivity (95% CI), specificity (95% CI), Area Under the Curve (AUC) and Youden index (J). Legend: J = (Se + Sp) − 1; n = samples number, + = positive sample, − = negative sample. Positive and negative predictive values (PPV and NPV, respectively) were calculated on the basis of the index value, excluding the indeterminate value samples (2 urine and 3 serum samples in negative control group, and 8 urine and 16 serum samples in positive group, had an indeterminate index between 0.8 and 1.1) and using the following equations: NPV = true negative/false negative + true negative and PPV = true positive/false positive + true positive. CI: confidence interval.

Sample	AUC	p-Value	Cut-Off (Abs)	Se	95%CI	Sp	95%CI	J	PPV	NPV
URINE	0.9841	<0.0001	>0.1900	91.11	84.99% to 95.32%	100.0	83.89% to 100.0%	0.9111	1.000	0.679
SERUM	0.9722	<0.0001	>0.7525	83.70	76.37% to 89.50%	100.0	83.16% to 100.0%	0.7525	1.000	0.607