AB0722 ULTRASOUND HALO COUNT IN THE DIFFERENTIAL DIAGNOSIS OF ATHEROSCLEROSIS AND LARGE VESSEL GIANT CELL ARTERITIS

Abstract

BackgroundGiant cell arteritis (GCA) is the most common vasculitis in the elderly and large vessel involvement occurs in up to 50% of cases. Otherwise, atherosclerosis is frequent in older patients; therefore, ultrasound (US) diagnosis of GCA in these patients may be challenging.ObjectivesTo determine the diagnostic discriminant validity between large vessel giant cell arteritis (LV-GCA) and atherosclerosis using US with intima-media thickness (IMT) measurements.MethodsWe included 44 patients, paired by age and sex, 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 ≥1mm was accepted as pathological.ResultsThe 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. Mean IMT values of all arteries included were significantly higher in LV-GCA than in atherosclerosis. The frequency and localization data are shown in Table 1. Among LV-GCA patients IMT ≥1mm was seen in 31 axillary, 30 subclavian and 28 CCA. In the atherosclerotic cohort, 17 (38.6%) had IMT ≥1mm 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 cut-off point of at least 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 in front of atherosclerosis.ConclusionThe IMT is higher in LV-GCA than in atherosclerosis. The proposed US halo count achieves an accuracy >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.*This study was presented in November 2022 at the ACR Convergence.