MO478: The Epidemiology of Anca-Associated Vasculitis at a Single Centre Over Two Decades
Authors: Storrar Josh , Alderson Helen , Brown Nina , O'riordan Edmond , Sinha Smeeta , Kalra Philip A 
Published: May 2022

Abstract

BACKGROUND AND AIMS
ANCA-associated vasculitis (AAV) refers to a group of conditions in which the end result is systemic injury of small blood vessels, resulting in damage to distinct organ systems including the lung, kidneys, ear, nose and throat. A characteristic, although not exclusive feature, is the development of anti-neutrophil cytoplasmic antibodies (ANCA) against specific proteins within the neutrophil-leucocyte proteinase 3 (PR3) and myeloperoxidase (MPO). The incidence varies according to geographic location but is ∼20 cases/million/year. The age of onset is usually between 45–75 years old, with a male: female ratio of 1:1. Without treatment, it is life-threatening; the aim of treatment is to induce remission with a strong immunosuppressive induction regimen followed by a maintenance phase. The risk of relapse remains. Here, we assessed the epidemiology of AAV &gt;2 decades at our centre (Salford Royal Hospital, UK) with particular reference to severity of disease at presentation, ANCA positivity and outcomes.

METHOD
Patients with a diagnosis of AAV (either granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) or eosinophilic granulomatosis with polyangiitis (EGPA)) were identified from our database between January 2000 and December 2021 (see Figure 1). Diagnosis was based on clinical features, ANCA result and kidney biopsy findings. A total of 47 were excluded and demographic data, co-morbidities, laboratory values (including baseline creatinine, eGFR, proteinuria, ANCA positivity), treatment given and outcomes were collected in the remaining sample. Analysis determined (i) basic demographic description of our cohort, (ii) median baseline creatinine, eGFR and proteinuria, (iii) those with an initial requirement for renal replacement therapy (RRT) at presentation, (iv) ANCA positivity rates and (v) outcomes including progression to RRT and mortality.

RESULTS
The evaluable cohort totalled 369 patients (see Table 1). Of these, 194 were male (52.6%), and the median age at presentation was 73 (IQR 60–82) years; 91.9% were Caucasian. Median baseline creatinine was 165 µmol/L (93–338), eGFR 33 mL/min/1.73 m2 (15–66) and proteinuria 98 g/mol (25–258). ANCA was measured in 363 (98.4%), of which c-ANCA and or PR3 positivity was seen in 142 (39.1%), and p-ANCA and or MPO positivity was seen in 148 (40.8%). In a small number, atypical ANCA was seen (1.9%) or ANCA was obscured by anti-nuclear factor (ANF) (2.8%). An immediate requirement for RRT at presentation was seen in 26 (7%). Progression to RRT at any time point over the follow up period was observed in 86 (23.3%), with the first RRT modality being haemodialysis in 64 (17.3%), peritoneal dialysis in 20 (5.4%) and transplant in 2 (0.5%). A total of 147 patients (39.8%) died over the follow-up period. A combined outcome of progression to RRT or death was seen in 191 (51.8%).

CONCLUSION
We show that patients present with AAV at an advanced age and with significant renal involvement (median baseline eGFR of 33 mL/min/1.73 m2 in our study). The distribution of PR3 and MPO positive vasculitis is similar, although there were a significant number of ANCA negative patients in our cohort. There were differences in concordance between c-ANCA and PR3 positivity, along with p-ANCA and MPO positivity, which may be explained by historical differences in testing. There remains a significant risk of progression to the requirement for RRT or death: 51.8% observed over our follow-up period of two decades.