Giant cell arteritis Investigation Initial investigations Obtain the following initial investigations in patients with suspected or confirmed GCA: CBC serum creatinine and urea serum electrolytes LFTs CRP and ESR urinalysis CXR other relevant investigations to exclude mimicking conditions. Diagnosis Suspect large-vessel GCA in patients with prominent systemic symptoms, limb claudication or persistently high inflammatory markers despite adequate corticosteroid therapy. B Assess for the predictive features of ischemic neuro-ophthalmic complications of GCA. B ACR/EULAR diagnostic criteria for giant cell arteritis Entry criteria Evidence of medium- or large-vessel vasculitis on imaging Alternative diagnoses mimicking vasculitis are excluded Age 50 years at the time of diagnosis Clinical criteria Morning stiffness in shoulders/neck Sudden visual loss Jaw or tongue claudication New temporal headache Scalp tenderness Abnormal examination of the temporal artery (absent or diminished pulse, tenderness, or hard "cord-like" appearance) Laboratory, imaging, and biopsy criteria Maximum ESR 50 mm/hour or maximum CRP 10 mg/L before initiation of treatment Positive temporal artery biopsy or halo sign on temporal artery ultrasound Bilateral axillary involvement (luminal damage, such as stenosis, occlusion, or aneurysm) FDG-positron emission tomography activity throughout descending thoracic and abdominal aorta (FDG uptake in the arterial wall greater than liver uptake by visual inspection) Diagnostic criteria are met Temporal artery biopsy Consider either performing a temporal artery biopsy at least 1 cm in length or obtaining an ultrasound of the temporal and axillary arteries, or both, to confirm the diagnosis in patients with suspected GCA. B Diagnostic imaging BSR Q Does the patient have prominent systemic symptoms? Q Does the patient have limb claudication? Q Does the patient have persistently elevated inflammatory markers despite adequate glucocorticosteroid therapy? Q Does the patient have other symptoms or signs suggestive of large-vessel giant cell arteritis? No to all Continue management and follow-up as clinically appropriate. Yes to any Obtain a confirmatory diagnostic test in patients with suspected GCA. Consider either obtaining an ultrasound of the temporal and axillary arteries or performing a temporal artery biopsy, or both. B Consider obtaining 18F-FDG-positron emission tomography, MRA, CT angiography, or axillary artery ultrasound for the evaluation of the involvement of the aorta and its proximal branches. C