Performance of the new 2022 ACR/EULAR classification criteria for giant cell arteritis in clinical practice in relation to its clinical phenotypes

To examine the performance of the new 2022 American College of Rheumatology (ACR)/EULAR classification criteria for giant cell arteritis (GCA) in routine clinical care, compared with the 1990 ACR GCA classification criteria. The fulfilment of 2022 ACR/EULAR and 1990 ACR criteria was tested in our real-life cohort of GCA patients with proven vasculitis by temporal artery biopsy or imaging (a necessary pre-requisite to apply the new criteria is the presence of a confirmed diagnosis of medium- or large-vessel vasculitis). The performance of classification criteria was evaluated in all patients with GCA across different subsets of the disease. Patients with GCA were compared with unselected controls with suspected GCA. A total of 136 patients with proven GCA were identified. The new criteria had a sensitivity of 92.6% and a specificity of 85.2%. According to the clinical phenotypes, the sensitivity was 98.8% in cranial GCA, 92% in extracranial large vessel (LV) GCA and 75% in occult systemic GCA. These data are much better than those observed with the 1990 ACR classification criteria, which showed a sensitivity of 66.1% and a specificity of 85.1% for the total sample, with a sensitivity of 89.1% in cranial GCA, 24% in extracranial LV-GCA and 35.7% in occult systemic GCA. Ten (7.4%) patients in our cohort did not fulfil either of the criteria sets (8 with occult systemic GCA and 2 with extracranial LV-GCA). The sensitivity of the new criteria in patients with occult systemic and extracranial LV-GCA could be greatly improved assigning more weight (3 points) to some imaging findings (axillary involvement and FDG-PET activity throughout the aorta). Our study confirms that the new classification criteria are more sensitive in real-life settings than the old ACR criteria across all clinical phenotypes.