O40 Trends in incidence of GCA in the UK

Abstract Background Giant cell arteritis (GCA) is the most common form of medium and large vessel vasculitis. Diagnosis remains difficult since there are a multitude of symptoms experienced by patients with GCA and if not promptly identified or treated, patients with GCA are at risk of irreversible visual loss. Therefore, a clear understanding of recent trends in incidence is important for clinicians, researchers and policy-holders to better understand and address future healthcare resource needs. Our objective was to estimate the annual UK incidence of GCA and assess whether this is changing over time. Methods We used the Clinical Practice Research Datalink (CPRD), a database of routinely recorded primary care records from across the UK. CPRD is representative of the UK population and contains patient information from approximately 15% of the UK population. For each year from 1992-2017, the number of patients with a first Read coded record of GCA in that year, and aged 40 years or older at the time of diagnosis, was determined. The annual denominator population included the registered practice population without a prior record of GCA, aged 40 years or older. Annual incidence per 10,000 person-years (P-Y) at risk was derived overall and stratified by age, gender and region of the UK. Trends over time were modelled using Joinpoint regression. To be confident of the primary care diagnosis of GCA, a sensitivity analysis was undertaken which included a prescription of corticosteroids alongside the GCA Read code. Results There was a decrease in annual incidence of GCA in the UK between 1992 and 2017. Incidence was highest in 1994 (2.29/10,000 P-Y; 95% CI: 1.96, 2.67). This decreased to 1.51/10,000 P-Y in 2006, after which the incidence rates stabilised. Incidence rates for women were higher than men, irrespective of year. Incidence peaked between 70 and 89 years of age, with females aged 70-79 having the highest overall incidence rate of 5.20/10,000 P-Y (95% CI: 5.00, 5.40). The region of the UK with the highest incidence rate of GCA from 2015-2017 was Yorkshire & the Humber with 2.63/10,000 P-Y. The regions with the lowest incidence of 1.13/10,000 P-Y were the North East and West Midlands. Sensitivity analysis gave similar patterns. Conclusion The incidence of GCA in the UK has decreased slightly in recent years, which may reflect developments in more definitive early GCA diagnosis through fast-track clinics and improvements in imaging. However, further research into the presenting features of GCA in primary care is required. A set of early clinical features and comorbidities that are positively associated and predictive of a subsequent diagnosis of GCA would improve diagnosis and avert significant complications associated with delayed treatment. Disclosures L.A. Barnett None. T. Helliwell None. K. Jordan None. J. Prior None.