Table 4.

Computation of Cut-off values using Mean +-2Sd and Mean +-3Sd.

Analysis	Antibody	# negatives	95% CI	Cut Off Point (Se, Sp)
Mean +-2 Standard Deviations	S-IgG	205	(-0.192, 0.487)	0.487 (92.45%, 95.12%)
	S-IgM	206	(-0.260, 0.739)	0.739 (69.35%, 95.14%)
	S-IgA	206	(-0.142, 0.185)	0.185 (100%, 97.09%)
	N-IgG	207	(-0.223, 0.874)	0.874 (45.19%, 93.24%)
	N-IgM	207	(-0.105, 0.701)	0.701 (3.85%, 95.17%)
	N-IgA	207	(-0.109, 0.345)	0.345 (62.16%, 98.07%)
	RBD-IgG	203	(-0.143, 0.264)	0.264 (87.06%, 96.55%)
	RBD-IgM	203	(-0.233, 0.681)	0.681 (27.27%, 93.60%)
	RBD-IgA	203	(-0.022, 0.057)	0.057 (100%, 97.54%)
Analysis		Variable	Mean ± 3SD	Cut-off Point (Se,Sp)
Mean ± 3 Standard Deviations	S-IgG	205	(-0.361, 0.656)	0.656 (82.08%, 98.05%)
	S-IgM	206	(-0.509, 0.989)	0.989 (51.61%, 98.06%)
	S-IgA	206	(-0.224, 0.267)	0.267 (92.16%, 99.03%)
	N-IgG	207	(-0.498, 1.149)	1.149 (30.77%, 98.55%)
	N-IgA	207	(-0.222, 0.458)	0.458 (48.65%, 98.55%)
	RBD-IgG	203	(-0.244, 0.365)	0.365 (72.94%, 98.03%)
	RBD-IgM	203	(-0.461, 0.910)	0.910 (12.72%, 97.04%)
	RBD-IgA	203	(-0.042, 0.077)	0.077 (100%, 98.03%)

Se, Sensitivity; Sp, Specificity.