International consensus statement on testing and reporting of antineutrophil cytoplasmic antibodies (ANCA)

Antineutrophil cytoplasmic antibody (ANCA) tests are used to diagnose and m onitor inflammatory activity in the primary systemic small vessel vasculiti des. ANCA is best demonstrated in these diseases by using a combination of indirect immunofluorescence (IIF) of normal peripheral blood neutrophils an d enzyme-linked immunosorbent assays (ELISAs) that detect ANCA specific for proteinase 3 (PR3) or myeloperoxidase (MPO). For ANCA testing in "new" pat ients, IIF must be performed on all serum samples. Serum samples containing ANCA, any other cytoplasmic florescence, or an antinuclear antibody (ANA) that results in homogeneous or peripheral nuclear fluorescence then should be tested in ELISAs for PR3-ANCA and MPO-ANCA. Optimally, ELISAs for PR3-AN CA and MPO-ANCA should be performed on all serum samples. Inclusion of the most recent positive sample in the IIF or ELISA may help demonstrate a chan ge in antibody level. Reports should use recommended terms. Any report of p ositive neutrophil fluorescence issued before the ELISA results are availab le should indicate that positive fluorescence alone is not specific for the diagnosis of Wegener granulomatosis or microscopic polyangiitis and that d ecisions about treatment should not be based solely on the ANCA results.