MPO and vasculitis: HR: Hazard ratio; ANCA: Anti-neutrophil cytoplasmic antibody; MPO-ANCA: Myeloperoxidase- ANCA; PLEX: Plasma exchange; PR3-ANCA: Proteinase 3– ANCA; RPGN: Rapidly progressive glomerulonephritis; ESRD: End-stage renal disease; MP: Methylprednisolone; EUVAS: European vasculitis study group; PLEX: Plasma exchange; IV: Intravenous; CYC: Cyclophosphamide; BVAS: Birmingham Vasculitis Activity Score; CRP: C-reactive protein; RITUXVAS: Rituximab versus cyclophosphamide in ANCA associated vasculitis; GCs: Glucocorticoids; GTI: Glucocorticoid toxicity index