Assessing Vasculitis in Giant Cell Arteritis by Ultrasound: Results of OMERACT Patient-based Reliability Exercises

Objective: To test the reliability of Outcome Measures in Rheumatology Clinical Trials (OMERACT) consensus-based ultrasound definitions for normal and vasculitic temporal and axillary arteries in patients with giant cell arteritis (GCA) and in controls. Methods: A preliminary 1-day meeting and a full 3-day meeting fulfilling OMERACT Ultrasound Group guidelines were held. Temporal and axillary arteries were examined at 2 timepoints by 12 sonographers on 4 patients with GCA and 2 controls. The aim was to test inter- and intrareader reliability for normal findings, halo sign, and compression sign. In both meetings, patients had established GCA. Pathology was more recent in the full meeting, which was preceded by 6 h of training. Scanning time was 15-20 min instead of 10-13 min. Results: In the preliminary exercise, interreader reliabilities were fair to moderate for the overall diagnosis of GCA (Light k 0.29-0.51), and poor to fair for identifying vasculitis in the respective anatomical segments (Light k 0.02-0.46). Intrareader reliabilities were moderate (Cohen k 0.32-0.64). In the main exercise, interreader reliability was good to excellent (Light k 0.76-0.86) for the overall diagnosis of GCA, and moderate to good (Light k 0.46-0.71) for identifying vasculitis in the respective anatomical segments. Intrareader reliability was excellent for diagnosis of GCA (Cohen k 0.91) and good (Cohen k 0.71-0.80) for the anatomical segments. Conclusion: OMERACT-derived definitions of halo and compression signs of temporal and axillary arteries are reliable in recent-onset GCA if experienced sonographers (> 300 examinations) have 15-20 min for a standardized examination with prior training and apply > 15 MHz probes.