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. 2021 Apr;7(2):e001555.
doi: 10.1136/rmdopen-2020-001555.

ANCA-associated renal vasculitis is associated with rurality but not seasonality or deprivation in a complete national cohort study

Oshorenua Aiyegbusi  1 , Marina Frleta-Gilchrist  2 , Jamie P Traynor  2 , Bruce Mackinnon  3 , Samira Bell  4 , Robert W Hunter  5 , Neeraj Dhaun  5 , Dana Kidder  6 , Graham Stewart  7 , Nicola Joss  8 , Michael Kelly  9 , Shahzad Shah  10 , Vishal Dey  11 , Kate Buck  12 , Kathryn I Stevens  2 , Colin C Geddes  2 , Emily P McQuarrie  2 ; Scottish Renal Biopsy Registry
Affiliations

ANCA-associated renal vasculitis is associated with rurality but not seasonality or deprivation in a complete national cohort study

Oshorenua Aiyegbusi et al. RMD Open. 2021 Apr.

Abstract

Background: Small studies suggest an association between ANCA-associated vasculitis (AAV) incidence and rurality, seasonality and socioeconomic deprivation. We examined the incidence of kidney biopsy-proven AAV and its relationship with these factors in the adult Scottish population.

Methods: Using the Scottish Renal Biopsy Registry, all adult native kidney biopsies performed between 2014 and 2018 with a diagnosis of granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) were identified. The Scottish Government Urban Rural Classification was used for rurality analysis. Seasons were defined as autumn (September-November), winter (December-February), spring (March-May) and summer (June-August). Patients were separated into quintiles of socioeconomic deprivation using the validated Scottish Index of Multiple Deprivation and incidence standardised to age. Estimated glomerular filtration rate and urine protein:creatinine ratio at time of biopsy were used to assess disease severity.

Results: 339 cases of renal AAV were identified, of which 62% had MPA and 38% had GPA diagnosis. AAV incidence was 15.1 per million population per year (pmp/year). Mean age was 66 years and 54% were female. Incidence of GPA (but not MPA) was positively associated with rurality (5.2, 8.4 and 9.1 pmp/year in 'urban', 'accessible remote' and 'rural remote' areas, respectively; p=0.04). The age-standardised incidence ratio was similar across all quintiles of deprivation (p=ns).

Conclusions: Seasonality and disease severity did not vary across AAV study groups. In this complete national cohort study, we observed a positive association between kidney biopsy-proven GPA and rurality.

Keywords: autoimmune diseases; epidemiology; granulomatosis with polyangiitis; immune system diseases; systemic vasculitis.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for submitted work; no financial relationships with any organisations that might have interes in submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1
Number of biopsies per million population per year for MPA and GPA within each rurality category, n=5 years (Scottish population – 82.9% urban, 11.21% accessible rural, 5.9% remote rural). P=0.04 for significant difference within GPA group. Category: series 1=urban; series 2=accessible rural; series 3=remote rural. AAV, ANCA-associated vasculitis; GPA, granulomatosis with polyangiitis; MPA, microscopic polyangiitis; PMP/year=per million population per year; error bars; SD.
Figure 2
Figure 2
Total number of patients with AAV on kidney biopsy by month (A) and season (B) across 5 years of the study (n=5). AAV, ANCA-associated vasculitis.
Figure 3
Figure 3
MPA and GPA crude incidence rate per million population per year adjusted for age, separated by SIMD quintile and age group. GPA, granulomatosis with polyangiitis; MPA, microscopic polyangiitis; Q1, most deprived; Q5, least deprived; SIMD, Scottish Index of Multiple Deprivation.
See this image and copyright information in PMC

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