Table 4

Concordance between immunoassays

	Control n=924	GPA n=186	MPA n=65
PR3-ANCA
Positive with all eight immunoassays	2	132	2
Negative with all eight immunoassays	871	33	57
Concordance	0.94	0.89	0.91
Positive with all assays after exclusion of CytoBead	2	133	2
Negative with all assays after exclusion of CytoBead	882	33	57
Concordance	0.96	0.89	0.91
MPO-ANCA
Positive with all eight immunoassays	5	15	43
Negative with all eight immunoassays	860	158	7
Concordance	0.94	0.93	0.77
Positive with all assays after exclusion of CytoBead	9	16	48
Negative with all assays after exclusion of CytoBead	882	162	7
Concordance	0.96	0.96	0.85

ANCA, antineutrophil cytoplasmic antibodies; GPA, granulomatosis with polyangiitis; MPA, microscopic polyangiitis; MPO, myeloperoxidase; PR3, proteinase 3.