Retrospective study on the epidemiology of antineutrophil cytoplasmic autoantibodies-associated vasculitis in two Australian health districts

Background ANCA-associated vasculitis (AAV) is more prevalent in rural Australia compared to metropolitan areas suggesting a role of environment in disease pathogenesis. However, the prevalence of environmental risk factors in Australian AAV patients has not been described. Aims To compare the incidence of AAV between two health districts (Illawarra Shoalhaven local health district (ISLHD), a mixed rural/metropolitan region, and South Eastern Sydney local health district (SESLHD), a metropolitan region) in Australia and its relationship to environmental exposures. Methods Cases of AAV from 2002 to 2017 were retrospectively identified from ISLHD and SESLHD using electronic medical records. Eligible participants were invited to complete a standardised questionnaire examining their exposure to silica, solvents, metal, dust, farming, gardening, and sunlight. Results 156 cases of AAV were identified from 2002 to 2017. A higher cumulative incidence of AAV was observed in the ISLHD (184.2 [95% confidence interval (CI) 143.6-232.7] per million) compared to SESLHD (102.6 [95% CI 82.1-126.8] per million). Over 50% of the cohort had high levels of silica and solvents exposure, based on self-reported questionnaires. There was no significant relationship between region and exposure to silica (p=0.96), solvents (p=0.44), metal (p=0.33), dust (p=0.25), farming (p=0.90), gardening (p=0.93), or sunlight (p=0.55). Conclusions We found a higher incidence of AAV in ISLHD compared to SESLHD with high levels of exposure to silica and solvents in both regions based on self-reported questionnaires. Prospective systematic collection of data, such as a registry of AAV, is warranted to further explore the relationship between environmental exposures and AAV. This article is protected by copyright. All rights reserved.