Disease flares, damage accrual and survival in ANCA-associated vasculitis in Western Australia

Background: ANCA-associated vasculitis (AAV) is a potentially life-threatening condition for which limited Australian data are available. We investigated the clinical and epidemiological outcomes of AAV in the last decade in a tertiary setting in Western Australia (WA). Methods and findings: A single centre observational study of patients fulfilling classification criteria for granulomatous polyangiitis (GPA), eosinophilic polyangiitis (EGPA) and microscopic polyangiitis (MPA) between 2007-2016. Clinical data collected at baseline, flares and last follow-up included disease activity (BVAS), treatment regimen and damage (VDI) scores. Non-parametric tests and Kaplan Meyer survival estimates were used in analysis. Results: During the study period there were 54 incident and 13 prevalent cases for an annual AAV incidence rate of 10.1/million (95% CI: 7.6-13.8) with rates for GPA (n=35), MPA (n=12) and EGPA (n=7) at 6.5, 2.2 and 1.3 per million respectively. Point prevalence per 1/1/2016 was 116.7/million. Age and gender distribution were similar between subtypes, but baseline BVAS scores were significantly higher in MPA patients (16 vs 10 vs 10, p<0.01). The relapse rate (0.4 per patient-year) was equivalent across AAV subtypes with less than 30% of patients in remission and damage accrual present in 93% at last followup. Patient survival (93.2% at 5 years) was negatively impacted especially by damage accrual with VDI >3. Conclusion: The incidence of especially GPA in WA is lower than in surrounding regions. Although current management of AAV leads to good short-term survival, it associates with frequent development of organ damage, which impacts on survival.