[Anti-neutrophil cytoplasmic antibody--enzyme immunosorbent assay]

Enzyme immunosorbent assay(ELISA) is a very useful method to determine anti-neutrophil cytoplasmic antibody(ANCA), which is an important serological marker for pauci-immune type systemic vasculitis and necrotizing glomerulonephritis. A test was made using new myeloperoxidase(MPO)-ANCA ELISA(A), employing native MPO purified from the neutrophils in sputum as a liquid phase antigen. Furthermore, the ELISA(B) using MPO, composed of one large and one small subunit, was tested as solid phase antigen. The intra-assay and inter-assay CV of the new ELISA(A) were 3.92 to 6.75% and 5.0 to 8.1%, respectively. Close ANCA titer correlation was shown between the new MPO-ANCA ELISA(A) and the conventional ELISA, using native MPO from peripheral neutrophils as solid phase antigen. ELISA(B) showed low MPO-ANCA detection sensitivity compared to ELISA(A) and to conventional ELISA. ELISA using native MPO from neutrophils in sputum as liquid phase antigen is useful for MPO-ANCA detection. There might be an ANCA which recognizes only native form MPO.