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Summary Background Temporal artery biopsy is considered the diagnostic gold standard for giant cell arteritis, despite approximately 39% of patients who are negative for the condition by biopsy subsequently being given a clinical diagnosis of giant cell arteritis. We aimed to assess the diagnostic accuracy of ultrasound examination in patients with suspected giant cell arteritis. Methods In this prospective, multicentre, non-interventional, cohort study (evaluation of ultrasound's role in patients suspected of having extracranial and cranial giant cell arteritis; EUREKA), we consecutively recruited patients aged 50 years or older, with clinically suspected giant cell arteritis from three Danish hospitals (South West Jutland Hospital in Esbjerg, Silkeborg Regional Hospital, and Rigshospitalet, Glostrup). Participants had a bilateral ultrasound of the temporal, facial, common carotid, and axillary arteries. Ultrasounds were done by ultrasonographers who were systematically trained in vascular ultrasound using appropriate equipment and settings. Participants then had a temporal artery biopsy within 7 days of initiation of corticosteroid treatment. A blinded ultrasound expert assessed all ultrasound images. Ultrasound vasculitis was defined in cranial arteries as a homogeneous, hypoechoic, intimamedia complex thickness and a positive compression sign and as a homogeneous intimamedia complex of 1 mm in thickness or wider in the axillary arteries and of 1·5 mm thickness or wider in the common carotid artery. Participants were followed up at 6 months. During this 6 month period, clinicians were able to collect data from all clinical examinations to enable a full clinical diagnosis at 6 months. Clinical diagnosis was based on the expert opinion of the treating rheumatologist. The diagnostic criterion standard was diagnosis confirmed after 6 months of follow-up. We used logistic regression analyses to calculate the odds ratio and 95% CI of ultrasound as a predictor for giant cell arteritis. Findings Between April 1, 2014, and July 31, 2017, 118 patients were screened for inclusion, of whom 106 had both ultrasound examinations and an eligible temporal artery biopsy and were included in the intention-to-diagnose population. The mean age was 72·7 years (SD 7·9), 63 (59%) participants were women, and 43 (41%) were men. Temporal artery biopsy was positive in 46 (43%) of 106 patients, and 62 (58%) of 106 patients had a clinically confirmed diagnosis of giant cell arteritis at 6 months (temporal artery biopsy sensitivity 74% [95% CI 62–84], specificity 100% [95% CI 92–100]). Cranial artery ultrasound was positive in all patients who had a positive temporal artery biopsy, and seven (58%) of 12 patients who were positive by ultrasound and negative by temporal artery biopsy were confirmed to have large-vessel giant cell arteritis via other imaging methods. The sensitivity of ultrasound diagnosis of giant cell arteritis was 94% (84–98) and specificity was 84% (70–93). Logistic regression analysis confirmed that ultrasound was the strongest baseline predictor for a clinically confirmed diagnosis of giant cell arteritis at 6 months (crude odds ratio 76·6 [95% CI 21·0–280·0]; adjusted for sex and age 141·0 [27·0–743·0]). Interpretation Vascular ultrasound might effectively replace temporal artery biopsy as a first-line diagnostic method in patients suspected of having giant cell arteritis when done by systematically trained ultrasonographers using appropriate equipment and settings. Funding The Institute for Regional Research at Hospital of Southwest Jutland, Esbjerg, Denmark.

Objectives To define chronic ultrasound lesions of the axillary artery (AA) in long-standing giant cell arteritis (GCA) and to evaluate the reliability of the new ultrasound definition in a web-based exercise. Methods A structured Delphi, involving an expert panel of the Large Vessel Vasculitis subgroup of the Outcome Measures in Rheumatology (OMERACT) Ultrasound Working Group was carried out. The reliability of the new definition was tested in a 2-round web-based exercise involving 23 experts and using 50 still images each from AA of long-standing and acute GCA patients, as well as 50 images from healthy individuals. Results The final OMERACT ultrasound definition of chronic changes was based on measurement and appearance of the intima-media complex. The overall reliability of the new definition for chronic ultrasound changes in longstanding GCA of the AA was good to excellent with Light's kappa values of 0.79-0.80 for inter-reader reliability and mean Light's-kappa of 0.88 for intra-reader reliability. The mean inter-rater and intra-rater agreements were 86-87% and 92%, respectively. Good reliabilities were observed comparing the vessels with longstanding versus acute GCA with a mean agreement and kappa values of 81% and 0.63, respectively. Conclusion The new OMERACT ultrasound definition for chronic vasculitis of the AA in GCA revealed a good to excellent inter- and intra-reader reliability in a web-based exercise of experts.

Background: Temporal artery biopsy (TAB) is considered the diagnostic gold standard for giant cell arteritis (GCA), despite up to 39% of biopsy-negative patients receiving a clinical diagnosis of GCA. This is a prospective, multicentre study assessing the diagnostic utility of ultrasound examination in patients with suspected GCA. Methods: Participants were recruited from three Danish centres among patients with clinically suspected GCA. Temporal (TA), facial (FA), common carotid (CC), and axillary arteries (AA) were examined by ultrasonographers, systematically trained in vascular ultrasound, using appropriate equipment and settings, before TAB. A blinded ultrasound expert evaluated all images. The primary outcome was the proportion of participants with clinically diagnosed GCA confirmed after 6-month follow-up. Ultrasound vasculitis was defined in cranial arteries as increased, hypoechoic intima-media thickness (IMT) and a positive compression sign, in large vessels as homogeneous IMT ≥ 1 mm in the AA and ≥1·5 mm in the CA. Findings: One hundred six patients were included in the intention-to-survey population. TAB was positive in 46 patients (43%), and 64 (60%) patients had a clinically confirmed diagnosis of GCA at 6-month follow-up (TAB sensitivity 74%, 95% CI 62–84%, specificity 100%, 95% CI 92–100%). Cranial artery ultrasound was positive in all TAB-positive patients. The sensitivity and specificity of the ultrasound diagnosis of clinical GCA were 94% (84–98%) and 84% (70–93%). Logistic regression analysis confirmed that ultrasound was the strongest baseline predictor for a clinically confirmed diagnosis of GCA at 6 months (crude: OR 76·6, 21·0–280·0; Adjusted for sex and age OR=141·0, 27·0–743). Interpretation: Vascular ultrasound can effectively replace TAB as a first-line diagnostic modality in patients suspected of having GCA when applied by systematically trained ultrasonographers using appropriate equipment and settings. Funding: None to declare. Declaration of Interest: None to declare. Ethical Approval: Written consent was obtained from all participating patients according to the Declaration of Helsinki. The study was approved by The Regional Committees on Health Research Ethics for Southern Denmark (reference number S-2014003) and the Danish Data Protection Agency (reference number 2008-58-0035).