Ultrasound Can Effectively Replace Temporal Artery Biopsy in the Diagnosis of Giant Cell Arteritis: A Multicentre, Prospective Cohort Study

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).