Background/Purpose: Giant cell arteritis (GCA) is the most common form of large vessel vasculitis. Prompt diagnosis and treatment of GCA is vital to prevent vision loss. The European League Against Rheumatism (EULAR) recommends ultrasound as the preferred imaging modality for GCA, and in subjects with positive imaging findings and a high clinical suspicion, diagnosis can be made without temporal artery biopsy (TAB). Fast track clinics (FTC) evolved in European countries to diagnose GCA through the use of ultrasound. However, the American College of Rheumatology (ACR) does not yet endorse the use of ultrasound for diagnosis, and FTCs in the United States are still relatively new. We present the results of the largest cohort of subjects reported to date referred to a United States FTC for the diagnosis of GCA.

Methods: Subjects referred to the FTC from November, 2017 – April 2021 were triaged by an attending rheumatologist who arranged for urgent rheumatology consultation and ultrasound and/or TAB. A protocolized ultrasound for the evaluation of GCA was performed by a trained vascular sonographer. The first 43 subjects referred to the FTC received both TAB and ultrasound. After demonstrating concordance between ultrasound and TAB, in subsequent referrals TAB was not performed in the setting of high clinical suspicion for GCA and positive ultrasound, or low suspicion for GCA and negative ultrasound. Ultrasound was considered positive for GCA if there was a halo sign with compression in the temporal arteries or if intima-media thickness (IMT) was increased in the large vessels.

Results: 209 subjects were referred to the FTC for ultrasound evaluation. 166 referrals were for evaluation of suspected new onset GCA, 16 were to evaluate for recurrent GCA, 18 were to evaluate concern for extracranial large vessel vasculitis, and 1 was to evaluate refractory PMR. The median time from referral to ultrasound was 1 day, with subjects on prednisone for 2 days prior to ultrasound. The time from referral to TAB was 7 days. 63 subjects were diagnosed with GCA. 209 subjects underwent ultrasound for GCA, and 51 were positive for GCA. Of the 51 positive ultrasounds, 25 had a positive halo sign and 35 had increased IMT of a large vessel. 69 subjects underwent TAB, and 9 were positive for GCA. Only one subject had a positive TAB and negative ultrasound, after IV methylprednisolone. Ultrasound identified evidence of vasculitis in 12 of 59 subjects with negative TAB. 10 subjects were diagnosed with GCA on clinical grounds alone despite negative TAB and/or ultrasound. 7 subjects diagnosed with GCA had permanent vision loss at the time of referral to the FTC. No subjects developed permanent vision loss following referral to the FTC. 3 subjects diagnosed with GCA died.

Conclusion: This FTC in the United States used ultrasound to successfully facilitate the diagnosis of GCA. Subjects received ultrasound rapidly following referral to the FTC and received prednisone for a short duration prior to ultrasound. Ultrasound frequently identified evidence of vasculitis in subjects with negative TAB.

Table 1 describes baseline clinical characteristics and outcomes. Median (IQR) reported for continuous variables. Abbreviations: FTC, fast track clinic; GCA, giant cell arteritis; IQR, interquartile range; TAB, temporal artery biopsy

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/vascular-ultrasound-for-giant-cell-arteritis-an-effective-diagnostic-modality-for-a-fast-track-clinic-in-the-united-states/