Incidence of giant cell arteritis in six districts of Paris, France (2015-2017).

This prospective population-based study estimated the incidence of giant cell arteritis (GCA) in northeastern Paris. GCA cases diagnosed between 2015 and 2017 were obtained from local hospital and community-based physicians and the national health insurance system database. Criteria for inclusion were living in the study area at that time and fulfilling the 1990 American College of Rheumatology classification criteria and/or its expanded version. Cranial and large-vessel GCA cases were defined by the presence or absence of cranial signs and/or symptoms, respectively. Annual incidence was calculated by dividing the number of incident cases by the size of the study population ≥ 50 years old. Completeness of case ascertainment was assessed by a three-source capture-recapture analysis. Among the 62 included cases, 42 (68%) were women, mean (± SD) age 77.3 ± 9.1 years. The annual incidence of GCA in northeastern Paris and completeness of case ascertainment were estimated at 7.6 (95% CI 5.9-9.8) per 100,000 inhabitants ≥ 50 years old and 66% (95% CI 52-92%), respectively. Incidence increased with age, peaked at age 80-89 years, and was almost twice as high in women versus men. Large-vessel GCA cases, mean (± SD) age 68.6 ± 11.5 years, accounted for 8% of all GCA cases. In this study, GCA epidemiology was mainly driven by cases with cranial GCA signs or symptoms and incidence results were consistent with recent European and past French studies.