MPO and kidney failure: In a subgroup analysis of 23 patients (16 MPO-ANCA positive and 7 PR3-ANCA positive) with severely reduced kidney function or kidney failure at diagnosis and available paired data (eGFR) at 12 months postdiagnosis, we found that 56% (9/16) of MPO-ANCA seropositive participants showed improvement in kidney function from KDIGO stages 4–5 at diagnosis to KDIGO stage 3 for 31% of individuals and stages 1–2 for an additional 25% by 1 year (figure 4D).