Table 3.

Daily rates of IgM and IgG positivity (based on cutoff values).

		Survivor n (%)	Non-survivor n (%)	P value
Day 7	IgM-positive	–	–	–
	IgG-positive	13 (38.24)	1 (7.69)	0.07
Day 10	IgM-positive	20 (40.00)	1 (7.69)	0.04
	IgG-positive	–	–	–
Day 12	IgM-positive	22 (47.83)	1 (7.14)	0.01
	IgG-positive	21 (45.65)	1 (7.14)	0.01
Day 14	IgM-positive	18 (40.00)	0 (0.00)	0.03
	IgG-positive	25 (55.56)	2 (13.33)	0.01

IgG positivity (day 7) is defined as IgG (day 7) ≥ 0.02 (0.02 is obtained from the ROC curve).

IgM positivity (day 10) is defined as IgM (day 10) ≥ 0.08 (0.02 is obtained from the ROC curve).

IgM positivity (day 12) is defined as IgM (day 12) ≥ 0.11 (0.11 is obtained from the ROC curve).

IgG positivity (day 12) is defined as IgG (day 12) ≥ 0.58 (0.58 is obtained from the ROC curve).

IgM positivity (day 14) is defined as IgM (day 14) ≥ 0.27 (0.27 is obtained from the ROC curve).

IgG positivity (day 14) is defined as IgG (day 14) ≥ 1.65 (1.65 is obtained from the ROC curve).

There are no differences in IgM (day 7) and IgG (day 10) between survivors and non-survivors. Therefore, the cutoff values for IgM (day 7) or IgG (day 10) are not set, and positivity rates are not set.

Fisher’s test is conducted if sample numbers are less than 5.

P < 0.05 indicates statistical significance.

Ig immunoglobulin, ROC receiver operating curve.