Impact of Proteinase 3 versus Myeloperoxidase Positivity on Risk of End-Stage Renal Disease in ANCA-Associated Glomerulonephritis Stratified by Histological Classification: A Population-Based Cohort Study

BACKGROUND: End-stage renal disease (ESRD) risk in patients with antineutrophil cytoplasmic antibody- (ANCA-) associated glomerulonephritis (ANCA-GN) according to ANCA serotype and stratified by histological classification has not been previously investigated. METHODS: Patients from the Norwegian Kidney Biopsy Registry (NKBR) between 1991 and 2012 who had biopsy-verified pauci-immune glomerulonephritis and positive antineutrophil cytoplasmic antibody serology were included. Cases with ESRD during follow-up were identified in the Norwegian Renal Registry. ESRD-free survival with proteinase 3 (PR3) versus myeloperoxidase- (MPO-) ANCA positivity stratified into 4 histological classes was investigated. RESULTS: Three hundred fifty-eight patients, of whom 87 progressed to ESRD during follow-up, were included. Patients with PR3- as compared to MPO-ANCA were younger (58 versus 64 years, p = 0.001), had a higher percentage of males (62 versus 41%, p < 0.001), had a lower percentage with a sclerozing glomerulonephritis pattern (4 versus 16%, p < 0.001), and had a significantly higher cumulative ESRD-free survival (90 versus 80%, p = 0.007) at 1-year follow-up. No significant differences in cumulative ESRD-free survival with PR3- as compared to MPO-ANCA were observed by histological stratification. CONCLUSION: Advanced glomerular sclerosis is found more frequently in patients with MPO-ANCA, explaining the higher risk of ESRD. ANCA serotypes have no impact on prognosis of patients with similar histological findings.