#5010 INCIDENCE AND CLINICAL PRESENTATION OF ANCA ASSOCIATED VASCULITIS AMONGST INDO-ASIAN PATIENTS IN LANCASHIRE, UK
Authors: Floyd Lauren , Morris Adam , Dhaygude Ajay 
Published: June 2023

Abstract

Background and Aims
ANCA associated vasculitis (AAV) is a rare autoimmune condition that is predominately seen in white Caucasian populations [1]. Across the UK, Europe and the USA, the prevalence of AAV is between 4.6 -18.4 per 100,000. Studies have shown significant geographical differences in the presentation and phenotype of AAV. PR3 positivity and granulomatosis with polyangiitis (GPA) is more common in Northern European countries at higher latitudes. In contrast MPO positivity is seen more frequently in Japanese, Chinese and Southern European populations [1]. Comparatively, few studies have looked at the incidence, phenotype and outcomes in ethnic minority patients in particular Indo-Asian populations.

Method
We completed a retrospective cohort study of patients with AAV from a central referral centre in Lancashire, UK between December 2010 and December 2022. Patients with a diagnosis of AAV according to the Chapel Hill consensus conference and who belonged to the following ethic groups; ‘Indian, British Indian, Pakistani, British Pakistani, Asian or Asian British’, were included. Using data from the 2021 census, available from the Office of National Statistics, denominator populations were obtained [2]. Patients ethnic group were determined by self-reported ethnicity records on hospital e-health records or via GP summary care records. Ethical approval was obtained (IRAS 257174).

Results
Using 2021 census data, the total population of Lancashire (Fig. 1), aged &gt;18 years old was 1,149,826. Of this population, the majority identified as white (1,059,000) and the second most common ethnic group was Asian / Asian British (74,523). Black/ African/ Caribbean/ Black British made up &lt;1% of the population and mixed / multiple ethnic groups and other ethnic groups made up just over 1%. Eighteen Indo-Asian patients with newly diagnosed AAV were identified. The mean age was 46 ±16.7 yrs, which is younger than our cohort of white patients who had a mean age of 65.1 ± 14.6 yrs. There was an equal gender split, the majority were PR3 positive (n = 12, 67%) and 6 patients had MPO positive AAV. Nine patients had renal involvement, with only 2 having renal limited disease and 1 requiring dialysis at presentation. Over half of the patients (n = 11, 61%) had ENT involvement. The crude incidence of AAV in Indo-Asian patients in Lancashire was 20.1 per million person years (95% CI 10.7, 28.5). This is higher than that reported in other areas of the UK [3]. When compared to age and gender matched white patients, white patients had more renal involvement (89.5% V's 50%, P = 0.01) and more renal limited disease (31.6% V's 11.1% P = 0.13). Pulmonary involvement was similar between the ethnic groups whereas ENT involvement was more prevalent in Indo-Asian patients (61.1% V's 26.3%, P = 0.03).

Conclusion
Our findings demonstrate that whilst the crude incidence of AAV is lower in Indo-Asian populations compared to white Caucasians, there is a significantly high incidence rate in the Lancashire area, which is greater than in other areas of the UK. Pearce et al. reported an incidence of 10.6 per million person years in Nottingham which was almost half that seen in our cohort [3]. Our Indo-Asian patients were on average younger and had less renal involvement compared to our cohort white patients. This contrasts some studies which report Indo-Asian populations to have more PR3 positivity and higher rates or renal involvement [1]. This may reflect an under diagnosis of extra renal disease and non-renal phenotypes in Indian subcontinent populations. There remains a gap in our understanding as to the genetic role in the pathogenesis and clinical phenotype of AAV disease. Further research is needed to determine if the differences seen between ethnic minorities are due to genetic or environmental factors.