Table 1.

Results from the SPRIA and ImmunoCAP 100 anti-ESA IgG4 assays and a cell-based assay for neutralizing antibodies^a

Sample	SPRIA			ImmunoCAP 100		Patient classification based on NAb assay
	Result	Isotype(s)	Anti-ESA Ab (ng/ml)	Result	Anti-ESA IgG4 Ab (ng/ml)
1	Positive	IgG1, IgG2, IgG3, IgG4	>10,000	Positive	145	amPRCA
2	Negative			Negative		Non-PRCA
3	Positive	IgG1, IgG2, IgG4	6,030	Positive	89	amPRCA
4	Positive	IgG1, IgG2, IgG4	620	Positive	89	amPRCA
5	Positive	IgG1, IgG2, IgG3, IgG4	>10,000	Positive	669	amPRCA
6	Negative			Negative		Non-PRCA
7	Positive	IgG1	600	Negative		Non-PRCA
8	Positive	IgG1 (IgG4b)	1,730	Positive	95	amPRCA
9	Negative			Negative		Non-PRCA
10	Negative			Negative		Non-PRCA
11	Negative			Negative		Non-PRCA
12	Negative			Negative		Non-PRCA
13	Positive	Unable to determine	340	Negative		Non-PRCA
14	Negative			Negative		Non-PRCA
15	Negative			Negative		Non-PRCA
16	Positive	Unable to determine	520	Positive	59	amPRCA
17	Positive	IgG1	6,860	Negative		amPRCA
18	Positive	IgG1	840	Positive	18	Non-PRCA
19	Positive	IgG1	3,690	Negative		Non-PRCA
20	Positive	IgM	920	Negative		Non-PRCA
21	Positive	IgG1	1,210	Negative		Non-PRCA
22	Positive	IgM	1.94	Negative		Non-PRCA
23	Positive	IgG3	700	Negative		Non-PRCA
24	Positive	IgG1	0.93	Negative		Non-PRCA
25	Positive	IgG1, IgG2, IgG3, IgG4	>10,000	Positive	4,978	amPRCA

^aAll patient samples that had an anti-ESA concentration of greater than 250 ng/ml by SPRIA were further characterized for isotype (IgG1, IgG2, IgG3, IgG4, and IgM) and tested in a cell-based bioassay to determine if neutralizing antibodies were present. All patient samples were tested in the ImmunoCAP anti-ESA IgG4 assay. All samples that that had less than 15 ng/ml of anti-ESA IgG4 were reported as negative.

^bThis patient tested anti-ESA IgG4 antibody positive at a subsequent time point.