TABLE 2.

Screening results of the nine U.S. serology standard candidate samples across seven different ELISAs^c

Subject IDb	Collaborative study panel IDs	Sample type	FNLCR			Source of methoda
						Krammer, RBD IgG (OD)	CDC
			Spike IgM (AU/mL)	Spike IgG (AU/mL)	Nucleocapsid IgG (AU/mL)		Spike pan-Ig (OD)	Spike IgM (titer)	Spike IgG (titer)
Subject 1		Plasma	230.2	923.3	6,240.1	2.4	2.7	100	1,600
Subject 2*	COV8, COV11	Plasma	201.6	4,971	15,838.9	2.8	2.8	100	6,400
Subject 3	COV13, COV15	Plasma	NEG	NEG	NEG	0.1	0.04	NEG	NEG
Subject 4	COV6, COV14	Plasma	610.8	12,281.5	10,813.7	2.8	2.7	1,600	6,400
Subject 5		Plasma	NEG	295.8	647.1	1.6	2.8	NEG	400
Subject 6*	COV5, COV12	Plasma	473.1	5,319.1	12,356.2	2.7	2.7	100	6,400
Subject 7*	COV9, COV16	Plasma	1,195	13,597.1	16,618.8	3.3	1.8	1,600	6,400
Subject 8		Plasma	116.1	814.2	4,146.9	2.1	2.8	100	400
Subject 9*	COV2, COV10	Plasma	124.7	31,893.3	20,297.7	2.8	2.8	400	6,400

^aThese assays were tested at FNLCR using protocols provided by Florian Krammer's lab and the CDC.

^bAsterisks indicate that samples 2, 6, 7, and 9 were pooled to develop the U.S. serology standard. For the collaborative study panel, COV1 and COV4 were assigned to the pooled U.S. serology standard, and COV3 and COV7 samples were assigned to an additional seronegative plasma sample collected prior to 2020, which was not included in the screening set of samples described in this table.

^cID, identifier; AU, arbitrary units; NEG, negative; OD, optical density.