Epidemiology of ANCA vasculitis in northern Spain

Objectives The incidence of anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) shows disparate results due to variable classification criteria and heterogeneous population series. We aimed to estimate the incidence of AAV in a well-defined population with standardized classification criteria.Methods This was a population-based study of AAV patients diagnosed from January 2000 to December 2023 in Cantabria, northern Spain. Patients were classified according to ACR/EULAR 2022 into granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), or unclassified vasculitis if the criteria were not met. Eosinophilic granulomatosis with polyangiitis patients were not included. The annual incidence rates were estimated by cases over 1 000 000 (106) (95% CI) including overall AVV, type of AAV, sex and year of diagnosis. A literature review was also performed.Results We included 152 patients [80M/72F; mean age 70.6 (13.18) years]. They were classified as MPA (67; 44%), GPA (64; 42.2%), and unclassified vasculitis (21; 13.8%). Annual incidence was 13.4 (95% CI: 10, 16.8)/106 [male 14.5 (95% CI: 10.5, 18.5); female 12.1 (95% CI: 8.7, 15.6)]. The Annual incidence of MPA was 5.9 (95% CI: 4, 7.8)/106 and GPA 5.6 (95% CI: 3.9, 7.3)/106. The mean annual incidence increased from 6.1 (95% CI: 4.5, 7.7)/106 to 16.5 (595% CI: .6, 27.4)/106 in the last 3 years, particularly in GPA from 2.3 (95% CI: 0.3, 4.9)/106 to 8.2 (95% CI: 2, 14.5)/106. The prevalence of AAV was 184.7 (95% CI: 181, 188)/106.Conclusion During a 20-year period we found that the incidence of AAV (GPA and MPA) in northern Spain was higher than in southern Spain, but lower than northern European countries. An increase in the incidence was observed in the last years. Graphical Abstract