Special remarks:

Anti-MPO is an indirect solid phase enzyme immunoassay (ELISA) for the quantitative measurement of IgG class autoantibodies against myeloperoxidase (MPO) in human serum or plasma. The assay is intended for in vitro diagnostic use only as an aid in the diagnosis of certain autoimmune vasculitides such as microscopic polyarteritis and crescentic glomerulonephritis.

Anti-neutrophilic-cytoplasma antibodies (ANCA) represents a group of autoantibodies directed towards the cytoplasmatic components of the neutrophilic granulocytes and monocytes. The classical methods for the determination of ANCA are the immunofluorescent methods. With these indirect immunofluorescence techniques two main patterns are recognized, a cytoplasmatic (c-ANCA) and a perinuclear (p-ANCA) type. The main antigen for the c-ANCA is the proteinase 3 (PR3), which is a serine proteinase of the present in primary granules. Antibodies of p-ANCA positive sera are mainly directed to myeloperoxidase (MPO). Antibodies to other antigens e.g. lactoferrin, elastase, cathepsin-G and also lysozyme often result in a similar p-ANCA pattern. Beside different untypical variants of p-ANCA IF patterns granulocyte specific antinuclear antibodies (GS-ANA) is indistinguishable from p-ANCA. This makes a clear interpretation and classification of the IF patterns difficult. Therefore every positive IF-ANCA findings esp. p-ANCA should be differenciated by ELISA techniques using purified antigens. PR3-ANCA and MPO-ANCA are reliable serologic markers in the diagnostics of vasculitides. PR3-ANCA is the classical autoantigen in Wegener´s granulomatosis with a clinical specificity of more than 95%. c-ANCA is documented to be present in different diseases. The target antigen myeloperoxidase is mainly present (70%) in microscopic polyangiitis.