Evaluation of revised classification criteria for giant cell arteritis and its clinical phenotypes.

BACKGROUND Giant cell arteritis (GCA) is a systemic vasculitis of the elderly, viewed by many as a disease with multiple and overlapping clinical phenotypes. Retrospective studies have shown differences in clinical presentation between these phenotypes. To reflect the heterogeneity of GCA, and novel diagnostic methods, new classification criteria have been proposed. METHODS This is a retrospective study of newly diagnosed patients with GCA at the outpatient rheumatology clinics at Skane University Hospital (Malmo and Lund) between 2012 and 2018. All patients were evaluated using two sets of classification criteria-the American College of Rheumatology (ACR) classification criteria from 1990, and a proposed revision of these criteria requiring objective findings (positive biopsy or imaging) for classification. Patients were further classified as one of four widely used clinical phenotypes. RESULTS A total of 183 patients with a new diagnosis of GCA were identified. The diagnosis was confirmed by 1-2 experienced rheumatologists in 116 of these patients at review of medical records. The ACR criteria were more sensitive than the revised criteria (93.1% vs 72.4%), while the revised criteria had higher specificity (94.0% vs 28.4%). The revised criteria tended to have higher sensitivity in the phenotype with constitutional symptoms compared to cranial GCA (p = 0.08). CONCLUSION The specificity of the ACR classification criteria for GCA can be improved by using revised criteria requiring objective findings of vasculitis. In addition, the wider symptoms covered by the revised criteria may improve classification of patients with a phenotype characterized by constitutional symptoms.