Epidemiology and Clinical Features of Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis in a Multiethnic Tertiary Care Center Cohort

Objectives At our center, ANCA-associated vasculitis (AAV) is seen with increasing frequency. We have a multiethnic population for whom less information is known about AAV,[1,2] and sought to describe the demographic characteristics, diagnostic settings, and mortality of patients diagnosed with AAV at a single tertiary care center. Methods Records of all patients with AAV were abstracted from 2015-2025 from the electronic medical record at a single tertiary care center. Demographic data, including ethnicity by self-report, diagnostic setting, ANCA subtype (granulomatosis with polyangiitis [GPA], microscopic polyangiitis [MPA], and eosinophilic granulomatosis with polyangiitis [eGPA]), and vital status at last follow-up were included. Descriptive statistics were used to characterize the cohort and compare patients from different ethnic backgrounds and ANCA subtypes. Survival was compared using Cox proportional hazard models. Results A total of 334 patients were identified; 192 (58%) were female. Mean age at diagnosis was 53 years ±18; mean disease duration was 10 years ±7. 61% (n=202) of patients were White, 30% (n=101) Indigenous, 8% (n=26) Asian, and 1.5% other (n=5). 49% of patients were diagnosed in a hospital ward, 36% in ambulatory care, 9% in intensive care and unknown in 6%. GPA was diagnosed in 50% (n=167), MPA in 38% (n=128), and EGPA in 11 %. Males were more frequently diagnosed with EGPA (61%, 39% in females; p=0.12) and were older at diagnosis (56±17 years, females 51±19 years; p-0.011). Sixty-two patients (19%) died during the study period. Mean age at death was 61 ±19 years. Indigenous patients were younger at diagnosis (46±18 years; White = 56±18 years; Asian = 55±18 years; p<0.001). Indigenous patients were more often diagnosed with MPA (50%), compared to 34% of white patients and 30% of Asian patients (p = 0.029). More Indigenous patients had died by the end of the follow-up period (28%; White 14%, Asian 19%; p=0.028). Adjusted hazard ratio for mortality was 4.5 (95% CI 2.5-8.3, p<0.001) for Indigenous patients compared to White patients (Figure 1). Figure 1. Adjusted Survival from Disease Onset by Ethnic Group (p <0.001) Conclusion On initial exploratory analysis of a large single center cohort, AAV appears to affect all ethnicities proportionally. We found differences in onset age and AAV subtype between ethnicities, with Indigenous patients diagnosed at a younger age and more often with MPA. Mortality was overall high at 19% during the follow-up period, with adjusted mortality particularly high in Indigenous patients. More studies are needed to determine factors contributing to poor outcomes and differences between ethnic groups. References [1.] Henderson BA. Arthritis Care Res 2025;77:873-80. [2.] Mohammed AJ. Rheumatology 2020;59:iii42-50.