Incidence of primary large vessel vasculitis in Norfolk, UK from 2011 to 2020

To report the annual incidence of primary large vessel vasculitis (LVV) in the adult population of Norfolk County, UK, including giant cell arteritis (GCA) (in those ≥50 years) and Takayasu arteritis (TAK).

Individuals diagnosed by histology or imaging who lived in NR1-NR30 postcode districts were included. Validated criteria from 1990 and 2022 were applied for final classification. Population data were available from the Office of National Statistics, UK.

270 individuals were diagnosed with primary LVV over 4.7 million person-years. The annual incidence (95% CI) of primary LVV was 57.5 (50.8, 64.7)/million person-years in the adult population. 227 and 244 individuals were diagnosed with GCA over ~2.5 million person-years using 1990 and 2022 criteria, respectively. The annual incidence (95% CI) of GCA was 91.6 (80.0, 104.3)/million person-years aged ≥50 years using 1990 criteria and 98.4 (86.4, 111.6)/million person-years aged ≥50 years using 2022 criteria. 13 and 2 individuals were diagnosed with TAK over 4.7 million person-years. The annual incidence (95% CI) of TAK was 2.8 (1.5, 4.7)/million person-years using 1990 criteria and 0.4 (0.0, 1.4)/million person-years using 2022 criteria, in the adult population. The incidence of GCA rose sharply in 2017 coincident with the introduction of a fast-track pathway and fell during the pandemic when the pathway was disrupted.

This is the first study that reports the incidence of objectively verified primary LVV in the adult population. The incidence of GCA may be affected by the availability of diagnostic pathways. The use of the 2022 classification criteria results in a rise in the classification of GCA and fall in that of TAK.