H. J. Farquhar, B. McGettigan, P. T. Chapman, J. L. O'Donnell, C. Frampton, L. K. Stamp

To determine the incidence of ANCA Associated Vasculitis (AAV) during the 3-year period before (period 1), and the 3 years following (period 2), the earthquake that occurred on 22 February 2011 in Christchurch, New Zealand. All ANCA tests performed in the Canterbury region for 3 years before the earthquake (period one, 2007-2010), and for 3 years after the earthquake (period two, 2011-2014) were examined. AAV was defined according to The European Medicines Agency classification algorithm. Medical records were reviewed and cases were included if they were newly diagnosed within the study period. Incidence was calculated using population data from the 2013 New Zealand census. 52 new cases of AAV were identified. The incidence in period one was 1.87/100,000/annum (95% C.I. 1.23 - 2.72), and for period two was 1.73/100,000/annum (95% C.I. 1.12 - 2.55). There was no statistically significant difference in incidence between the two study periods. There was no difference when analyzing by MPO or PR3 status, or restricting the analyses to those residing in an urban environment. The mean age at diagnosis for MPO AAV was significantly younger in period two than period one (61 years vs 71 years, p = 0.05). There were no other clinically important differences between the two groups. This study does not support the hypothesis that an environmental agent, caused by dust pollution related to earthquake damage, has a causative role in the pathogenesis of AAV.