Comparison of severity classification in Japanese patients with antineutrophil cytoplasmic antibody-associated vasculitis in a nationwide, prospective, inception cohort study

Objective: To compare disease severity classification systems for six-month outcome prediction in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods: Patients with newly diagnosed AAV from 53 tertiary institutions were enrolled. Six-month remission, overall survival, and end-stage renal disease (ESRD)-free survival were evaluated. Results: According to the European Vasculitis Study Group (EUVAS)-defined disease severity, the 321 enrolled patients were classified as follows: 14, localized; 71, early systemic; 170, generalized; and 66, severe disease. According to the rapidly progressive glomerulonephritis (RPGN) clinical grading system, the patients were divided as follows: 60, grade I; 178, grade II; 66, grade III; and 12, grade IV. According to the Five-Factor Score (FFS) 2009, 103, 109, and 109 patients had <= 1, 2, and >= 3 points, respectively. No significant difference in remission rates was found in any severity classification. The overall and ESRD-free survival rates significantly differed between grades I/II, III, and IV, regardless of renal involvement. Severe disease was a good predictor of six-month overall and ESRD-free survival. The FFS 2009 was useful to predict six-month ESRD-free survival but not overall survival. Conclusions: The RPGN grading system was more useful to predict six-month overall and ESRD-free survival than the EUVAS-defined severity or FFS 2009.