Background Giant cell arteritis (GCA) is the most common systemic vasculitis in adults aged 50 years or above. Annual incidence rates vary widely from 6.9–76.6 per 105 of adults in this age group, depending on the region.1
Objectives To determine the incidence rate of GCA in our population.
Methods We prospectively collected incident cases of GCA from January 1st 2011 to December 31st 2012 at our department of rheumatology which is a part of an integrated secondary/tertiary university teaching hospital that is the only referral center serving a region representing approximately a quarter of the national adult population. Additionally, newly diagnosed cases of GCA between January 1st 2009 and December 31st 2010 were retrospectively identified by searching the electronic patient records for ICD-10 codes M31.5 and M31.6 at our department. The retrospective approach and search strategy was also applied on electronic medical records at the departments of infectious diseases and ophthalmology between January 1st 2009 and December 31st 2012. To further reduce possibility of underreporting, the attached medical faculty's Institute of Pathology provided a list of all temporal artery biopsies examined during the observation period which were then cross-referenced with the hospital's electronic medical records. Annual incidence rate for GCA was then calculated.
Results During the four year observation period we identified 97 new cases of GCA (68% female; mean (SD) age 75.6 (8.1) years) from a well-defined adult white Caucasian population of 232,041 inhabitants aged 50 or above. The temporal artery biopsy was consistent with GCA, negative or not performed in 75.3%, 18.6, and 6.2% of cases, respectively. Thus, the annual incidence of GCA in our population is 10.5 (95% CI 8.5–12.7), and 4.7 (95% CI 3.8–5.7) per 105 adults aged 50, and 20 years or above, respectively.
Conclusions The annual incidence rate of 10.5 per 105 adults aged 50 or above makes GCA the most common systemic vasculitis in this age group of our population. Although the GCA almost exclusively affects adults over 50 years of age, the incidence rate of 4.7 per 105 adults aged 20 and above, also makes it the most common systemic vasculitis in the adult population overall, with IgA vasculitis coming a close second with 3.7 per 105 adults aged 20 years or above.
Gonzalez-Gay MA, Vazquez-Rodriguez TR, Lopez-Diaz MJ et al. Epidemiology of Giant Cell Arteritis and Polymyalgia Rheumatica. Arthritis Rheum 2009;61:1454-61.
Disclosure of Interest None declared