Table 2.

SPR assay for the detection of human IgG targeting the native, B.1.351, B.1.617.2, and P.1 spike proteins using serum from variant-naïve, SARS-CoV-2-positive individuals at weeks 4 and 16 post-diagnosis.

		Native spike		B.1.351 spike		B.1.617.2 spike		P.1 spike
		W4	W16	W4	W16	W4	W16	W4	W16
Shift (kRU)	Pos	1.5 ± 0.5	1.4 ± 0.6	1.1 ± 0.5	1.0 ± 0.5	1.1 ± 0.7	0.9 ± 0.5	0.8 ± 0.3	0.7 ± 0.3
Shift (kRU)	Neg	0.3 ± 0.2	0.1 ± 0.1	0.6 ± 0.3	0.2 ± 0.1	0.3 ± 0.3	0.3 ± 0.3	0.4 ± 0.2	0.5 ± 0.2
Threshold (kRU)		0.6	0.35	0.7	0.35	0.7	0.7	0.6	0.7
Positive sera	# Pos	31	31	26	27	22	17	27	16
	# Neg	1	0	6	4	9	14	5	15
Control sera	# Pos	0	0	1	0	1	1	1	1
	# Neg	8	8	7	8	7	7	6	6
AUC		0.99	0.99	0.82	0.93	0.87	0.83	0.90	0.75
P value		< 0.0001	< 0.0001	< 0.05	< 0.0001	< 0.01	< 0.01	< 0.001	< 0.05
Sensitivity		97	100	81	87	71	55	84	51
Specificity		100	100	88	100	88	88	86	86