TABLE 3.

Results of anti-SARS-CoV-2 antibody testing^a

			No. of results submitted to RfB that were:			Error rate data
Sample no.	EQA scheme no.	Target value	Positive (n)	Borderline (n)	Negative (n)	Total results reported (n)	Results evaluated as incorrect (n/%)
IgG
1	1	Positiveb	164	38	46	248	46/18.6%
2	1	Positive	237	0	11	248	11/4.4 %
3	1	Negative	4	0	244	248	4/1.6%
4	1	Negativeb	6	26	216	248	6/2.4%
5	2	Positivec	90	19	135	244	0/0%
6	2	Negative	1	0	243	244	1/0.4%
7	2	Negative	1	1	242	244	2/0.8%
8	2	Positive	239	1	4	244	5/2.1%
9	3	Positive	247	0	12	259	12/4.6%
10	3	Positivec	74	50	135	259	0/0%
11	3	Positive	251	0	8	259	8/3.1%
12	3	Negative	2	0	257	259	2/0.8%
IgA
5	2	Negative	0	7	54	61	7/11.5%
6	2	Negative	1	0	60	61	1/1.6%
7	2	Negative	9	11	41	61	20/32.8%
8	2	Positive	49	1	11	61	12/12.7%
9	3	Positive	46	0	16	62	16/25.8%
10	3	Positive	43	0	19	62	19/30.7%
11	3	Positive	47	0	15	62	15/24.2%
12	3	Negative	1	0	61	62	1/1.6%
IgM
1	1	Negative	9	4	49	62	13/20.9%
2	1	Negative	4	4	54	62	8/12.9%
3	1	Negative	3	2	57	62	5/8.1%
4	1	Negative	5	3	54	62	8/12.9%

^aRfB, Reference Institute for Bioanalytics; EQA, external quality assessment.

^bFor these samples, borderline results were considered conditionally correct.

^cFor these samples, all submitted results were considered conditionally correct.