FRI0672 INCIDENCE OF GIANT CELL ARTERITIS IN 6 DISTRICTS OF PARIS, FRANCE (2015–2017)

Abstract

Background Little is known about the current incidence of giant cell arteritis (GCA) in France. Objectives We conducted a prospective, population-based survey over 3 years to estimate the incidence of GCA in inhabitants of Paris, France. Methods From January 2015 to December 2017, new GCA diagnoses in 6 districts of northeastern Paris (257,888 inhabitants ≥50 years old) were prospectively identified by 1) biannual postal mails to 1,134 general practitioners and other specialists practicing in the study area; 2) quarterly e-mail surveys among 28 hospital departments located in or close to the study area and 3) new records in the National Health Insurance System database with code M31 (other necrotizing vasculopathies) in the International Classification of Diseases, 10th revision. Clinical data of notified cases were retrieved from medical records. Retained cases lived in the study area at the time of diagnosis, fulfilled the 1990 American College of Rheumatology classification criteria and/or were ≥50 years old, with imaging or histology evidence of large-vessel inflammation and increased levels of inflammatory biomarkers. Clinical presentations with no cranial symptoms were classified as large-vessel GCA and otherwise as cranial GCA. Annual incidence rates were calculated by dividing the number of incident cases by the size of the study population and the study period (in years); 95% confidence intervals (CIs) were calculated by using the Poisson distribution. Completeness of case ascertainment was assessed by a three-source capture–recapture analysis. Results Among 61 retained cases (69% females; mean age: 77.1 [SD: 9.0] years), 57 (93%) were cranial GCA and 4 (7%) large-vessel GCA. GCA diagnoses were supported by temporal artery biopsy findings, imaging of the aorta and its main branches, temporal artery ultrasonography and/or aortic tissue histology in 35 (57%), 18 (30%), 7 (11%), and 1 (2%) cases, respectively. GCA incidence rate (per 100,000 inhabitants ≥ 50 years old) was estimated at 7.9 cases (95% CI: 6.0–10.1). Completeness of case ascertainment was estimated at 66% (95% CI: 52–92%). Conclusion Our annual incidence estimate of GCA is close to the sole published estimate for another French population established 4 decades ago [1] and adds further support to the lower incidence of GCA in non-Scandinavian versus Scandinavian populations. Large-vessel GCA cases seem a rare form of GCA as compared with cranial GCA.