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Background: ANCA associated vasculitis (AAV) and Polyarteritis Nodosa (PAN) are primary systemic vasculitides with the potential to cause organ or life-threatening disease. Our centre serves as the secondary care provider for the county of Norfolk, UK. The annual incidence of Granulomatosis with Polyangiitis (GPA) and microscopic polyangiitis (MPA) in Norfolk between 1988 to 2010 was 11.3 (95% CI 9.1, 13.4) and 5.9 (4.4, 7.5) respectively, peaking at 31.4/million for GPA and 20.6/million for MPA between the ages of 65-74. The incidence of Eosinophilic granulomatosis with polyangiitis (EGPA) and PAN were not reported. Objectives: To describe the annual and age-specific incidence of AAV, (including GPA, MPA and EGPA as separate entities) and PAN in the county of Norfolk between 2011 and 2020. Methods: Patients with a new diagnosis of AAV or PAN between the years of 2011 and 2020, who were resident in the NR postal districts wholly contained within the county of Norfolk were included. Population data were available from the Office of National Statistics, UK. Incidence and confidence intervals were calculated using Byar's approximation for a Poisson distribution. The classification labels of the vasculitides were derived using the American College of Rheumatology (ACR) 1990 criteria for GPA, EGPA and PAN, Chapel Hill Consensus Conference (CHCC) definition for MPA, followed by reclassification according to the EMEA algorithm. Results: 164 individuals were diagnosed with AAV and PAN (89 GPA, 60 MPA, 12 EGPA, 3 PAN) over 4.7 million-person years. 79 (48.2%) were female. Mean (SD) age at diagnosis was 67.5 (16.1). Of the 89 individuals with GPA 43 (48.3%) had PR3 ANCA positivity, 40 (45%) had MPO ANCA positivity and 6 (6.7%) were ANCA negative. Of the 60 individuals with MPA, 21 (35%) had PR3 ANCA positivity, 39 (65%) had MPO ANCA positivity, and none were ANCA negative. Of the 12 individuals with EGPA, 1 (8.3%) had PR3 ANCA positivity, 6 (50.0%) had MPO ANCA positivity, and 5 (41.7%) were ANCA negative. The annual incidence (per million population) of GPA, MPA, EGPA and PAN was 18.9 (95% CI 15.2, 23.3), 12.8 (95% CI 9.7, 16.4), 2.6 (95% CI 1.3, 4.5), 0.6 (95% CI 0.1, 1.9) respectively. The annual incidence of all AAV was 34.3 (95% CI 29.2, 40.0) per million. The age specific annual incidence for GPA was highest in the 8th decade at 53.2 (95% CI 36.2, 75.6) per million and for MPA was highest in the 9th decade at 48.4 (95% CI 27.1, 79.8) per million. Conclusion: We report an update on the annual incidence of AAV and PAN in our county. In the 2010's there has been an increase in the annual incidence of GPA and MPA in the county of Norfolk, UK compared to historical data between 1988 to 2010. The incidence is comparable to our older data up to the 7th decade but continues to rise in the 8th and 9th decades. This may suggest improved ability to diagnose the disease in the elderly due to better diagnostics and increased awareness. REFERENCES: 1 Watts RA, Mooney J, Skinner J, Scott DG, Macgregor AJ. The contrasting epidemiology of granulomatosis with polyangiitis (Wegener's) and microscopic polyangiitis. Rheumatology (Oxford). 2012 May;51(5):926-31. Acknowledgements: NIL. Disclosure of Interests: None declared.
Mukhtyar et al. (Sat,) studied this question.