Background/Purpose At 1251 on 22 February 2011 a magnitude 6.4 earthquake struck Christchurch killing up to 185 people and causing widespread damage to buildings in the city centre and surrounds. Multiple building collapses during the busy lunchtime period in Christchurch when the earthquake occurred will have resulted in significant environmental exposures. Prominent involvement of the upper and lower respiratory tracts suggests that inhaled antigens may have a role in pathogenesis of ANCA associated vasculitis.  An increased incidence and severity of MPO positive vasculitis was observed after the Kobe earthquake in 1995. The aim of this study was to describe the incidence and characteristics of ANCA positive vasculitis before and after the 2011 Christchurch earthquake.

Methods All ANCA tests reported by Christchurch pathology centres over a 2 year period prior to February 21 2010 (period 1) and the 2 year period after February 22 2011 (period 2) were extracted from laboratory information systems. Clinical notes from patients with positive MPO or PR3 antibodies were reviewed to confirm newly diagnosed vasculitis cases who resided within the Christchurch area. Demographic information and organ involvement was confirmed on all newly diagnosed cases and compared between periods using Fisher’s exact and independent t-tests. Total Canterbury population was obtained from Statistics New Zealand.

Results In period 1, 2592 total ANCA requests were processed; of these 37 (1.4%) were MPO positive and 100 (3.9%) were PR3 positive. 13/37 (35%) patients were subsequently confirmed to have newly diagnosed MPO positive vasculitis and 9/100 (9%) patients were confirmed to have PR3 positive vasculitis. In period 2, 2416 total ANCA requests were processed; of these 32 (1.3%) were MPO positive and 118 (4.9%) were PR3 positive. 7/32 (21.9%) patients were confirmed to have newly diagnosed MPO positive vasculitis and 11/118 (9.3%) newly diagnosed PR3 positive vasculitis. The rate of MPO vasculitis per 100,000 population was 3.45 in period 1 and 1.93 in period 2 (RR 1.8 95%CI 0.66-5.29). The rate of PR3 vasculitis per 100,000 population was 2.39 in period 1 and 3.03 in period 2 (RR 0.79 95%CI 0.29-2.09). In the post-earthquake period those with a new diagnosis of MPO vasculitis were significantly younger than those diagnosed in the pre-earthquake period (Table1).

Conclusion In contrast to a previous study we have shown no statistically significant difference in rate of newly diagnosed MPO or PR3 positive vasculitis after a major earthquake. A longer study period post-earthquake may be required. The earlier age of onset of MPO vasculitis post-earthquake is of interest and may relate to younger people being in the areas of greatest building collapse in the city center. Further information of location at the time of the earthquake will be required.

Table 1: Demographic and clinical characteristics pre (period 1) and post (period 2) the 2011 Christchurch earthquake

PR3 vasculitis	Period 1 (n=9)	Period 2 (n=11)	p value
Age years; mean (SEM)	63.0 (5.2)	68.7 (4.4)	0.41
% male	100%	63.6%	0.09
PR3 mean (SEM)	1224 (550)	934.8 (360.5)	0.66
Renal involvement	5 (55.6%)	4 (36.4%)	0.65
Respiratory involvement	8 (88.9%)	8 (72.7%)	0.59
MPO vasculitis	Period 1 (n=13)	Period 2 (n=7)	p value
Age years; mean (SEM)	71.3 (2.9)	58.4 (5.3)	0.03
% male	10/13 (77%)	5/7 (71.4%)	1
MPO mean (SEM)	623.7 (199.4)	462.3 (154.6)	0.59
Renal involvement	11/13 (84.6%)	5/7 (71.4%)	0.59
Respiratory involvement	6/13 (46.2%)	2/7 (28.6%)	0.64

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/an-analysis-of-the-incidence-and-characteristics-of-anca-positive-vasculitis-before-and-after-the-christchurch-earthquake/