Association of atypical anti-neutrophil cytoplasmic antibody with comorbidities and outcome in a hospital-based population

Introduction: Atypical anti-neutrophil cytoplasmic antibody (a-ANCA) is characterized by a positive fluorescence staining other than typical cytoplasmic or perinuclear ANCA. ANCA is associated with increased risk of dialysis and mortality in patients with ANCA vasculitis. However, comorbidities related to a-ANCA and whether a-ANCA exhibits an increased risk for renal failure and mortality remain unclear. This study aimed to explore the comorbidities and outcome associated with a-ANCA. Materials and methods: This retrospective study enrolled 164 and 170 patients with typical ANCA and a-ANCA positivity, respectively, who visited Taichung Veterans General Hospital, Taiwan from January 2016 to March 2021. Logistic regression analysis was used to determine risk factors and the rheumatological diagnosis associated with a-ANCA. Cox proportional hazard regression and Kaplan–Meier curves were employed to identify variables associated with 5-year renal survival and mortality. Results: Patients with a-ANCA had lower chance of ANCA-associated vasculitis (OR: 0.02, 95 % CI: 0.01–0.07 p < 0.001), and systemic lupus erythematosus (OR: 0.23, 95 % CI: 0.11–0.48, p < 0.001), but a higher risk of rheumatoid arthritis (OR: 2.99, 95 % CI: 1.15–7.83, p = 0.025) and ulcerative colitis (OR: 5.50, 95 % CI: 1.20–25.29, p = 0.028). Patients with a-ANCA had a better renal survival (OR: 0.14, 95 % CI: 0.08–0.24, p < 0.001) and lower mortality (OR: 0.31, 95 % CI: 0.16–0.60, p = 0.001) than patents in the typical ANCA group. The 5-year renal survival and mortality was 89.3 % and 8.8 %, respectively, in patients with a-ANCA. Conclusion: Patients with a-ANCA had better renal survival and lower mortality rates compared to patients with typical ANCA. These real-world data provide evidence of the long-term outcome and shed light on avenues for the strategic management of patients with a-ANCA.