Ab0722 ultrasound halo count in the differential diagnosis of atherosclerosis and large vessel giant cell arteritis

Background Giant 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. Objectives To determine the diagnostic discriminant validity between large vessel giant cell arteritis (LV-GCA) and atherosclerosis using US with intima-media thickness (IMT) measurements. Methods We 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. 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. 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. Conclusion The 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. References [1]De Miguel E, Beltran LM, Monjo I, Deodati F, Schmidt WA, Garcia-Puig J. Atherosclerosis as a potential pitfall in the diagnosis of giant cell arteritis. Rheumatol (United Kingdom). 2018;57(2):318–21. [2]Schäfer VS, Juche A, Ramiro S, Krause A, Schmidt WA. Ultrasound cut-off values for intima-media thickness of temporal, facial and axillary arteries in giant cell arteritis. Rheumatol (United Kingdom). 2017. [3]Nielsen BD, Hansen IT, Keller KK, Therkildsen P, Gormsen LC, Hauge E-M. Diagnostic accuracy of ultrasound for detecting large-vessel giant cell arteritis using FDG PET/CT as the reference. Rheumatology (Oxford). 2020 Aug;59(8):2062–73. Table 1. Number of arteries with intima media thickness (IMT) ≥1 mm in GCA and atherosclerosis patients GCA (n=44) Atherosclerosis (n=42) Axillary Right 27 Right 2 Left 23 Left 1 Bilateral 19 Bilateral 1 Any 31 Any 2 Subclavian Right 20 Right 2 Left 25 Left 1 Bilateral 20 Bilateral 0 Any 30 Any 3 Common Carotid Distal Right 21 Right 8 Left 19 Left 11 Bilateral 12 Bilateral 5 Any 28 Any 14 Common Carotid Proximal Right 4 Right 3 Left 9 Left 3 Bilateral 2 Bilateral 1 Any 11 Any 5 Acknowledgements: NIL. Disclosure of Interests Irene Monjo Speakers bureau: Roche, Novartis, UCB, Gedeon. Richter, Consultant of: Roche, Elisa Fernández-Fernández: None declared, José María Mostaza: None declared, Carlos Lahoz: None declared, Juan Molina Collada: None declared, Eugenio de Miguel Speakers bureau: AbbVie, Novartis, Pfizer, MSD, BMS, UCB, Roche, Grünenthal, Janssen, Sanofi;, Paid instructor for: Janssen, Novartis, Roche, Consultant of: AbbVie, Novartis, Pfizer, Galapagos, Grant/research support from: AbbVie, Novartis, Pfizer.