Table 1

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

SampleSPRIAImmunoCAP 100Patient classification based on NAb assay
ResultIsotype(s)Anti-ESA Ab (ng/ml)ResultAnti-ESA IgG4 Ab (ng/ml)
1PositiveIgG1, IgG2, IgG3, IgG4>10,000Positive145amPRCA
2NegativeNegativeNon-PRCA
3PositiveIgG1, IgG2, IgG46,030Positive89amPRCA
4PositiveIgG1, IgG2, IgG4620Positive89amPRCA
5PositiveIgG1, IgG2, IgG3, IgG4>10,000Positive669amPRCA
6NegativeNegativeNon-PRCA
7PositiveIgG1600NegativeNon-PRCA
8PositiveIgG1 (IgG4b)1,730Positive95amPRCA
9NegativeNegativeNon-PRCA
10NegativeNegativeNon-PRCA
11NegativeNegativeNon-PRCA
12NegativeNegativeNon-PRCA
13PositiveUnable to determine340NegativeNon-PRCA
14NegativeNegativeNon-PRCA
15NegativeNegativeNon-PRCA
16PositiveUnable to determine520Positive59amPRCA
17PositiveIgG16,860NegativeamPRCA
18PositiveIgG1840Positive18Non-PRCA
19PositiveIgG13,690NegativeNon-PRCA
20PositiveIgM920NegativeNon-PRCA
21PositiveIgG11,210NegativeNon-PRCA
22PositiveIgM1.94NegativeNon-PRCA
23PositiveIgG3700NegativeNon-PRCA
24PositiveIgG10.93NegativeNon-PRCA
25PositiveIgG1, IgG2, IgG3, IgG4>10,000Positive4,978amPRCA
  • a All 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.

  • b This patient tested anti-ESA IgG4 antibody positive at a subsequent time point.