OMERACT GCA phantom projectSchremmer, Tobias (Avtor) Dejaco, Christian (Avtor) Recker, Florian (Avtor) Aschwanden, Markus J. (Avtor) Boumans, Dennis (Avtor) Bruyn, George A. W . (Avtor) Chrysidis, Stavros (Avtor) Daikeler, Thomas (Avtor) Dalsgaard Nielsen, Berit (Avtor) De Miguel, Eugenio (Avtor) Hočevar, Alojzija (Avtor) giant cell arteritisultrasonographyvasculitisObjective: Ultrasonography is crucial for diagnosing giant cell arteritis (GCA); however, training opportunities are rare. This study tested the reliability of ultrasonography findings and measurements of the intima-media thickness (IMT) among ultrasonography experts by using phantoms of the axillary (AA) and temporal arteries (TA) created with high-resolution 3D printing. Methods: Twenty-eight participants from 12 European countries received eight sets of phantoms of the AA and the superficial TA (including common, frontal and parietal branches), which were examined in a blinded fashion according to a predefined protocol and evaluated based on Outcome Measures in Rheumatology (OMERACT) GCA ultrasound definitions. Due to difficulties with the delineation of the intima-media complex, the parietal branch of the phantoms was modified, and a second round was conducted. The IMT was measured, and phantoms were classified as normal or vasculitic. Results: In both rounds, the phantoms were correctly classified as normal/abnormal in >81% of cases yielding a Fleiss' kappa of 0.80 (95% CI 0.78 to 0.81) in round 1 and 0.74 (95% CI 0.72 to 0.75) in round 2. IMT measurements revealed an intraclass correlation coefficient (ICC 1.1) of 0.98 (95% CI 0.98 to 0.99) in both rounds. Intrarater reliability was good with a median Cohens Kappa of 0.83 and median ICC of 0.78. Conclusion: The study demonstrated high reliability among ultrasound experts in applying the OMERACT ultrasound definitions for GCA and in measuring the IMT using a 3D-printed phantom of the AA and TA. This phantom could assist clinicians in training to assess the large arteries of patients with suspected or established GCA.20252026-06-01 14:15:53Neznano29620sl