LAUSR

There are no data on the collective incidence of the large vessel vasculitides. The incidence of GCA and Takayasu arteritis in the UK has been based on clinical coding in routine administrative datasets. There are no data on the incidence of these diseases based on clinically verfied diagnoses. We studied the incidence of the large vessel vasculitides in a stable population with a predominant Northern European ancestry. Individuals attending a secondary care hospital with a clinically verified diagnosis of primary systemic vasculitis made between 2011-2020, who lived within the NR postcode districts of Norfolk county were included if they met classification criteria for GCA or Takayasu arteritis, or had definite tissue or imaging evidence of large vessel vasculitis. Population above the age of 18 as in the 2011 census, available from the office of national statistics, was accepted as the denominator. If classification criteria for both GCA and TAK were met, physician judgement was accepted as final diagnosis. 272 adults were diagnosed with large vessel vasculitis out of a population of 454,316. The annual incidence of large vessel vasculitis in Norfolk is 59.9/million in the adult population. The annual incidence of GCA is 9.9/100,000 over the age of 50 using the ACR 1990 criteria and 10.6/100,000 using the ACR/EULAR 2022 criteria. The rise in the incidence from 2017 onwards coincides with the establishment of a fast-track pathway (Table 1). The dip in the incidence in 2020 coincides with suspension of services during the SARS-CoV-2 pandemic. The annual incidence peaks at 168.5/100,000 in the 9th decade and is commoner in females (12.3/100,000 vs 7.3/100,000). The annual incidence of Takayasu arteritis is 3.3/million in the adult population using the ACR 1990 criteria and 1.1/million using the ACR/EULAR 2022 criteria. This is the first study that reports the incidence of all objectively diagnosed large vessel vasculitis in a stable population in Norfolk county. The incidence of GCA rose with the establishment of a fast-track pathway and its peak may have been affected by the SARS-CoV-2 pandemic. GCA is commoner in females and peaks in the 8th and 9th decades. Disclosure C.B. Mukhtyar: None. C. Beadsmoore: None. F. Coath: None. G. Ducker: None. K. Sisson: None. R.A. Watts: None.