Epidemiology of primary systemic vasculitis in the Australian Capital Territory and south-eastern New South Wales

Abstract

Background: The aim of the study was to determine the epidemiology of primary systemic vasculitis in the Australian Capital Territory and the surrounding rural region between 1995 and 2005.

Methods: Cases were ascertained by a medical record search according to international consensus classification criteria. For antineutrophil cytoplasmic antibody-associated vasculitides, ascertainment was corroborated by a search of all positive antineutrophil cytoplasmic antibody serology during the study period. Denominators were obtained from region-specific census data collected during the study period. Prevalence, incidence and patient characteristics for primary systemic vasculitides were determined for two 5-year periods, 1995-1999 and 2000-2004.

Results: We identified 41 cases of primary systemic vasculitides (Wegener's granulomatosis (WG), microscopic polyangiitis (MPA), Churg-Strauss syndrome or polyarteritis nodosa) between 1995 and 1999 and 67 between 2000 and 2004, giving prevalences of 95/million (95% confidence interval (CI) 76.9-116.1) and 148/million (95%CI 125.1-173.9), respectively. Annual incidence was similar in both periods (approximately 17/year per million adult population). Disease-specific incidences (per million per year) for each of the two periods were 8.8 and 8.4 for WG, 2.3 and 5.0 for MPA, 2.3 and 2.2 for Churg-Strauss syndrome and 2.3 and 1.1 for polyarteritis nodosa. The rural incidence of MPA was 13.9 (95%CI 7.7-23.5) compared with 1.6 (95%CI 0.2-7.2) in the city and there was a trend towards a higher incidence of WG in rural than urban areas.

Conclusion: The overall incidence of primary systemic vasculitides is similar to that reported from other developed countries. WG is more common in south-eastern Australia than in southern Europe, whereas MPA is less common. There was a trend towards higher incidence of antineutrophil cytoplasmic antibody-associated vasculitides in rural than urban areas.