Ultrasound halo count in the differential diagnosis of atherosclerosis and large vessel giant cell arteritis

OBJECTIVE: To determine the diagnostic discriminant validity between large vessel giant cell arteritis (LV-GCA) and atherosclerosis using ultrasound (US) intima-media thickness (IMT) measurements. METHODS: We included 44 patients with LV-GCA and 42 with high-risk atherosclerosis. US examinations of the axillary, subclavian, and common carotid arteries (CCA) were systematically performed using a MylabX8 system (Genoa, Italy) with a 4–15-MHz probe. IMT ≥ 1 mm was accepted as pathological. RESULTS: The LV-GCA cohort included 24 females and 20 males with a mean age of 72.8 ± 7.6 years. The atherosclerosis group included 25 males and 17 females with a mean age of 70.8 ± 6.5 years. The mean IMT values of all arteries included were significantly higher in LV-GCA than in atherosclerosis. Among LV-GCA patients, IMT ≥ 1 mm was seen in 31 axillary, 30 subclavian, and 28 CCA. In the atherosclerotic cohort, 17 (38.6%) had IMT ≥ 1 mm with axillary involvement in 2 patients, subclavian in 3 patients, carotid distal in 14 patients (5 bilateral), and isolated carotid proximal affectation in 1 case. A cutoff point greater than 1 pathological vessel in the summative count of axillary and subclavian arteries or at least 3 vessels in the count of six vessels, including CCA, showed a precision upper 95% for GCA diagnosis. CONCLUSION: The IMT is higher in LV-GCA than in atherosclerosis. The proposed US halo count achieves an accuracy of > 95% for the differential diagnosis between LV-GCA and atherosclerosis. The axillary and subclavian arteries have higher discriminatory power, while carotid involvement is less specific in the differential diagnosis.