Objective: Vascular ultrasound has been increasingly used to diagnose giant cell arteritis (GCA). The temporal and axillary arteries are commonly evaluated. However, the usefulness of including the subclavian artery remains unclear. This study investigated whether inclusion of the subclavian artery in addition to the temporal and axillary arteries in the ultrasound evaluation of GCA improves the accuracy of the examination beyond ultrasonography of the temporal and axillary arteries alone.
Methods: We formed a fast-track clinic to use ultrasound to rapidly evaluate patients with suspected GCA. In this cohort study, patients referred for new concern for GCA received a vascular ultrasound for GCA. Subclavian intima-media thickness (IMT) cutoffs of 1.0 and 1.5 mm were retrospectively assessed.
Results: Two hundred thirty-seven patients were referred to the fast-track clinic from November 2017 to August 2021. One hundred sixty-eight patients received an ultrasound for concern for new GCA. With a subclavian IMT cutoff of 1.5 mm, inclusion of the subclavian artery did not identify any patients with GCA who were not otherwise found to have positive temporal and/or axillary artery examinations, and at this cutoff, there was 1 false-positive result. A subclavian IMT cutoff of 1.0 mm identified several subjects diagnosed with GCA who had otherwise negative ultrasounds, but most subjects with an isolated subclavian IMT greater than 1.0 mm had false-positive results, and the specificity of this cutoff was poor.
Conclusion: Inclusion of the subclavian artery in the ultrasound assessment of GCA at 2 different cutoffs rarely contributed to the accurate diagnosis of GCA and increased the rate of false-positive results.
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