Patients
A total of 40 patients with MPO-AAV enrolled in this study were all selected from the First Affiliated Hospital of Anhui Medical University from March 2017 to May 2020. Their AAV were diagnosed according to the classification criteria for GPA and EGPA published by American College of Rheumatology (ACR) in 1990 and the definition for MPA from 2012 Chapel Hill Consensus Conferences (CHCC) nomenclature of vasculitis[1, 24, 25]. All patients were test positive for p-ANCA and MPO-ANCA by indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA), respectively, and also with negative detection for c-ANCA and PR3-ANCA as well as anti-nuclear antibody (ANA). They were all diagnosed with MPO-AAV in active state for the first time. Their blood samples and clinical documents including disease activity assessment were taken before initiation of any immunosuppressive treatment. The Version 3 of Birmingham Vasculitis Activity Score (BVAS-V3) was employed to evaluate the vasculitis activity. In addition, 40 healthy volunteers were included in this study as controls. This study had been approved by the Ethics Committee of the First Affiliated Hospital of Anhui Medical University, and all subjects have signed informed written consent before enrolled.