Background The epidemiology of ANCA-associated vasculitis (AAV) varies geographically, due to both genetic and environmental factors. The epidemiology of AAV is well-described in White Caucasian populations in which there is an incidence of ∼20/million, although the relative incidence of granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) varies. Most studies suggest AAV is less common in Blacks and Asians, but there are no detailed epidemiological studies. However, preliminary data from West London in 2011 suggested that there was an increasing number of patients of Indo-Asian origin being diagnosed with AAV, comprising 20% of new referrals1.
Objectives To describe the epidemiology of AAV in a multi-ethnic population.
Methods Retrospective case note review of incident cases of ANCA +ve AAV within the urban area of Nottingham March 2007 – June 2013. Self-reported ethnicity was collected from hospital records. Incidence rates for different ethnic groups by age, sex were calculated using the 2011 census data for the denominator population. The area included had an adult (≥16 years) population of 451,056, and an ethnic breakdown of White 82.8%, mixed race 3.2%, Asian 8.8%, Black 4.3%, Other 1.0%.
Nottingham University Hospitals Trust is the central referral hospital for the denominator population. Patients were identified as part of a local institution approved audit of the management of AAV and included reviewing the notes of all patients with positive MPO/PR3 ANCA results. All diagnoses were confirmed by review of the hospital notes using the EMEA classification.
Incidence rates were calculated using the appropriate corresponding ethnic population as the denominator. 95% CI were calculated using the Poisson distribution for the observed number of cases.
Results Overall 53 incident cases of AAV occurred over the 6.25 year period. Annual incidence of AAV was 18.8/million (95% CI 14.1-24.6). Incidence of GPA, MPA and eosinophilic granulomatosis with polyangiitis (EGPA) were 6.7/million (4.1–10.5), 11.0/million (7.5–15.6) and 1.1/million (0.2–3.1) respectively.
Incidence of AAV among the White population was 21.4/million (15.9–28.2), and among the whole non-White population was 6.2 (1.3-18.1). Among the Black population the incidence was 16.7/million (2.0–60.2) and for the Indian subcontinent 6.1/million (0.2–33.9). There were no cases identified from South East Asian ethnicities or those of mixed race. The non-White cases were 1 Pakistani 65 yrs lady with MPO+ve MPA, 1 76 yrs Black Caribbean man with MPO+ve EGPA, and 1 48 yrs Black (not African, not Caribbean) man with PR3+ve MPA. We did not find any non-White cases of GPA.
There was a higher than expected proportion of MPO+ve patients (52.8%) compared to PR3+ve (45.3%), and 1 patient (1.9%) was p-ANCA+ve but MPO/PR3-ve.
Conclusions We conclude that AAV has a similar incidence in Whites, Asians and Blacks. It is possible that AAV may be lower in patients of non-White ethnicity and especially in Indian subcontinent ethnicities. GPA may be less common in non-Whites. The non-White population studied was small. These findings need confirmation in a larger multiethnic population.
Tanna A et al. The changing ethnic prevalence of ANCA associated vasculitis in London: Increasing Indo-Asian influence with critical differences in disease outcome. Renal Association Conference Proceedings 2011; Poster 263.
Disclosure of Interest None declared
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