Anti Neutrophil Cytoplasmic Antibodies (ANCA),

Detection of anti-neutrophil cytoplasmic antibodies (ANCA) is important for the diagnosis and monitoring of ANCA-associated vasculitis (AAV) which includes granulomatosis with polyangitis (Wegener’s granulomatosis); microscopic polyangitis eosinophilic granulomatosis with polyangitis (Churg-Strauss syndrome).
This is an indirect immunofluorescence (IIF) assay using ethanol fixed neutrophils as substrate. A number of IIF patterns are recognised including perinuclear (P-ANCA), cytoplasmic (C-ANCA) and atypical ANCA.
C-ANCA is usually associated with anti-PR3 specificity. P-ANCA may be associated with anti-MPO specificity. Other antigens recognised by ANCA include lactoferrin, lysozyme, cathepsin G and bacterial/permeability increasing (BPI) enzyme and usually associated with atypical ANCA patterns.
Because the immunofluorescence pattern is not antigen specific all positive ANCA patterns are further investigated with antigen specific ELISA for both anti-myeloperoxidase (MPO) and anti-proteinase 3 (PR3) which are the usual clinically significant specificities.