Criteria
The diagnosis of giant cell arteritis (GCA) is based on the presence of key clinical and laboratory features. The American College of Rheumatology (ACR) classification criteria were updated in 2022 by the ACR/European Alliance of Associations for Rheumatology (EULAR).[1] The criteria use a points-based system that draws on clinical, laboratory, imaging and biopsy findings. These criteria were developed for, and are best applied to, investigative studies of groups of patients. The criteria can be used to distinguish GCA from other forms of vasculitis, but were not developed as diagnostic criteria.
Requirements are that a diagnosis of medium or large vessel vasculitis has been made, mimics have been excluded and the patient is 50 years of age or older. A patient can then be classified as having GCA with a cumulative score of ≥6 points based on the following indicators:[1]
Positive temporal artery biopsy or temporal artery halo sign on ultrasound (+5)
Erythrocyte sedimentation rate ≥50 mm/hour or C reactive protein ≥10 mg/L (+3)
Sudden visual loss (+3)
Morning stiffness in shoulders or neck, jaw or tongue claudication, new temporal headache, scalp tenderness, temporal artery abnormality on vascular exam, bilateral axillary involvement on imaging and fluorodeoxyglucose-positron emission tomography activity throughout the aorta (+2 each).
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