Abstract
Anti-neutrophil cytoplasmic antibodies (ANCA) play a central role in the diagnosis and pathogenesis of patients with ANCA-associated vasculitis. ANCA-associated vasculitis is a rare disease characterized by necrotizing inflammation of small/medium-sized blood vessels with and without granuloma in different organs. The main syndromes are granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic GPA. ANCA in these diseases are almost always directed against proteinase 3 and myeloperoxidase. Most laboratories worldwide use as standard the indirect immunofluorescence technique 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 new testing strategy for ANCA in vasculitis directly identifies the ANCA target antigen and has a particular value for the AAV sub-classification. Recent studies have shown that AAV can be classified based on ANCA serotype. ANCA presence and the antigen specificity also may have important value as a prognostic factor and may serve as a guide for immunosuppressive therapy. The clinical utility of ANCA depends on the 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.
Highlights
The detection of anti-neutrophil cytoplasmic antibody (ANCA) as a diagnostic tool and marker of disease in Wegener’s granulomatosis was described in 1985 by Van der Woude and coworkers.[1]
Detection of ANCA in vasculitis is based on primary screening by immunofluorescence test (IFT) on ethanol-fixed neutrophils, and positive indirect immunofluorescence (IIF) test should always be followed by specific PR3- and MPO-ANCA immunoassays (Figure 1)
This review considers current data on ANCA testing, presents the new international consensus on ANCA testing, and discusses the usefulness of PR3- and MPO-ANCA in the diagnosing and managing of patients with small-vessel vasculitis
Summary
This work is licensed under and Creative Commons Attribution-NonCommercial 4.0 International License. Department of Internal Medicine, Rheumatology and Immunology, Vasculitis-Center Tübingen-Kirchheim, Medius Klinik Kirchheim, University of Tübingen, Kirchheim-Teck, Germany
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