A population-based study showing better renal prognosis for proteinase 3 antineutrophil cytoplasmic antibody (ANCA)-associated nephritis versus myeloperoxidase ANCA-associated nephritis.

OBJECTIVE: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is usually differentiated based on clinical phenotypes, but recent data indicate that myeloperoxidase (MPO)-AAV is genetically distinct from proteinase 3 (PR3)-AAV. We reviewed a population-based cohort of AAV, focusing on differences in clinical and laboratory characteristics and to compare renal outcome between MPO-ANCA and PR3-ANCA nephritis.

METHODS: All new cases of AAV diagnosed between 1997 and 2009 in a geographically defined area in southern Sweden were retrieved using a validated search algorithm. Data were collected from time of diagnosis and end of followup. Renal and patient survival were analyzed according to ANCA serotype.

RESULTS: During the study period, 201 patients were diagnosed with AAV, 98 tested positive for PR3-ANCA, and 85 for MPO-ANCA. Patients with PR3-ANCA were younger, had significantly higher inflammatory activity, and had a larger number of organs involved at diagnosis, but nephritis was more prevalent among patients with MPO-associated (72/85; 85%) versus PR3-associated disease (67/98, 68%). When comparing only patients with ANCA-associated nephritis, those with MPO-ANCA were more likely to develop endstage renal disease (n = 27, 38%) than those with PR3-ANCA (n = 10, 15%), p = 0.003. The risk remained significantly elevated after adjusting for sex, age, and s-creatinine level at diagnosis (HR 2.64; 95% CI 1.25-5.58; p = 0.003). There were no significant differences in mortality rates between the 2 groups.

CONCLUSION: The outcome in this population-based cohort indicates that among AAV patients with nephritis, renal prognosis is better in the PR3-ANCA group, even after adjustment for sex, age, and renal function at diagnosis.