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: 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 (EGPA) 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 (80/72 men; mean age; 70.6 ± 13.18 years) patients. They were classified as MPA (67; 44%), GPA (64; 42.2%), and unclassified vasculitis (21; 13.8%). Annual incidence was 13.4 (10-16.8)/106 [male 14.5 (10.5-18.5); female 12.1 (8.7-15.6)]. The Annual incidence of MPA was 5.9 (4-7.8)/106 and GPA 5.6 (3.9-7.3)/106. The mean Annual incidence increased from 6.1 (4.5-7.7)/106-16.5 (5.6-27.4)/106 in the last three years, particularly, in GPA from 2.3 (0.3-4.9)/106-8.2 (2-14.5)/106. The prevalence of AAV was 184.7 (181-188)/106.

Conclusion: During a 20-year period we found that the incidence of AAV (GPA and MPA) in Northern Spain is higher than Southern Spain, but lower than Northern European countries. An increase in the incidence was observed in the last years.