[ANCA-associated vasculitis: recent methodological advances for ANCA detection].

Anti-neutrophil cytoplasmic antibodies (ANCA) play a central role in the diagnostic and pathogenesis of patients with small vessel vasculitis, so called ANCA-associated vasculitis (AAV). ANCA in these diseases are almost always directed against proteinase 3 (PR3-ANCA) and myeloperoxidase (MPO-ANCA). Most laboratories worldwide use as standard the indirect immunofluorescence technique (IFT), on human neutrophils, to screen for ANCA, and then confirm positive IFT results with antigen specific immunoassyas for PR3- and MPO-ANCA. New guidelines for ANCA testing have been developed based on a recent European multicentre study, and according to the revised 2017 international consensus recommendations, testing for ANCA in small vessel vasculitis can be done by PR3- and MPO-ANCA immunoassays, without the categorical need for IIF. The clinical utility of ANCA depends on type of assay performed and the appropiate ordering of testing the right clinical setting. Accurate identification of all patients with AAV and the avoidance of misdiagnosis can be achieved using a "gating policy" based on clinical information given to the laboratory at the time of request.