MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: Whereas ANCA GN subtypes did not differ in age, gender, or systemic markers of AAV disease activity (C-reactive protein/CRP, Birmingham Vasculitis Activity Score/BVAS), MPO-ANCA GN was associated with more severe deterioration of kidney function as estimated by serum creatinine and loss of eGFR (Figure 2A–C).