ACR Convergence 2025| Video: Rheum for Everyone, Episode 26—Ableism

An official publication of the ACR and the ARP serving rheumatologists and rheumatology professionals

The Great Debate: Ultrasound vs. Temporal Artery Biopsy in Giant Cell Arteritis

Michael Cammarata, MD, RhMSUS  |  

CHICAGO—Temporal artery biopsy (TAB) has long been the gold standard for the diagnosis of giant cell arteritis (GCA). However, with continued advancements in ultrasound resolution and growing provider expertise, temporal artery ultrasound (TAUS) is increasingly being used in practice. This shift is reflected in the differing recommendations of the ACR/VF and EULAR guidelines, with the European guidelines now favoring ultrasound as the initial imaging modality.1,2 In the ACR Convergence 2025 session, Great Debate: Ultrasound vs. Temporal Artery Biopsy in Giant Cell Arteritis, two vasculitis experts went head to head to determine the ideal first test in the diagnosis GCA.

Ultrasound Should Replace Biopsy for GCA Diagnosis

Wolfgang Schmidt, MD, MACR, Professor of Charité University Medicine at Waldfriede Hospital, Berlin, was well suited to argue his position because he was the first to describe the ultrasound halo sign in GCA and pioneered the GCA fast-track clinic. Accordingly, he opened his presentation by making it clear that he felt strongly about encouraging clinicians to start with ultrasound to diagnose GCA.

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Dr. Schmidt made note of the change in practice patterns over the past two decades, with providers moving from TAB to TAUS, reflected in the fact that TAUS is recommended as the first-line imaging modality for GCA diagnosis in the updated EULAR guidelines for large vessel imaging.2

Using the ACR/EULAR classification criteria for GCA, he demonstrated that ultrasound has greater potential diagnostic yield. Although both positive TAB and TAUS represent five points on the criteria, confirmation of bilateral axillary involvement with ultrasound provides an additional two points toward the diagnosis.3

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He commented on many disadvantages to the temporal artery biopsy—the greatest being a delay in diagnosis, resulting in a period of uncertainty, sometimes over five days, and requiring additional patient contact once the results are finalized. Even once the results are in, there are data to suggest that providers do not alter their management. He highlighted a study that demonstrated that even in the setting of a negative biopsy, 87% of patients were continued on prednisone.4 Further, biopsies are invasive procedures involving removal of a portion of the artery, which confers risk of facial palsy and hematoma, although he acknowledged the overall incidence of these events is low.5

Dr. Schmidt contrasted these challenges with the ease of performing TAUS, which only requires about 10 minutes in experienced hands, even when performed bilaterally. With examination of the axillary arteries, ultrasound also has the unique ability to capture the approximately 20% of cases of isolated extra-cranial GCA.6 This begs the question, however: Are we missing other forms of extracranial GCA when only examining the temporal and axillary arteries via ultrasound? The answer appears to be rarely; only two of 72 patients had aortitis or iliac artery vasculitis in a study comparing TAUS and PET-CT.7

Unlike biopsy, repeat ultrasound can provide prognostic value. OMERACT developed the GCA ultrasound score (OGUS), which has demonstrated that higher scores at baseline portend higher risk of relapse in one year and decreases in scores after treatment are associated with decreased risk of relapse.8,9

Dr. Schmidt shared his success with GCA fast-track clinics, including their impact on reducing visual impairment.10 He outlined recommendations for establishing fast-track clinics, such as easy and rapid appointment scheduling, use of appropriate technology such as ultrasound probes with a frequency of at least 18 MHz, and collaboration with ophthalmology, neurology and radiology for imaging, such as MRI and PET-CT, as well as with surgeons to pursue biopsy if needed. The main barrier to entry, however, is his recommendation to have performed at least 50 ultrasounds of the temporal and axillary arteries—and ideally over 300.11

Dr. Schmidt closed with a convincing list of positive attributes for TAUS: It’s widely available, integrated into exam, fast and cost effective, patient friendly and repeatable, supported by excellent evidence, high resolution, able to detect subclinical GCA in PMR, and there is no need for referral.  Perhaps most convincingly, he emphasized how fun and satisfying it can be to provide patients with an immediate answer to their concerns.

Ultrasound Should Not Replace Biopsy for GCA Diagnosis

The counterargument was presented by Tanaz Kermani, MD, MS, professor of medicine and founder and director of the Vasculitis Program at the University of California, Los Angeles. Dr. Kermani presented on behalf of Peter Grayson, MD, MSc, senior investigator at the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), who was unfortunately unable to attend given the government shutdown at the time of ACR Convergence 2025.

Dr. Kermani conceded that ultrasound has its benefits, particularly that it is safe and cost effective and can be performed at the bedside. However, she noted that suspected diagnoses must be confirmed, that we should be particularly careful to avoid false positives, and that this is best done with biopsy.

She identified histology as the gold standard with 100% specificity and noted that other diseases, such as atherosclerosis and other forms of vasculitis, can cause the halo sign, leading to risk of misclassification as GCA. She also argued that the sensitivity of the halo sign, between 70 and 78%, was unsatisfactory and could lead to missed diagnoses of GCA.

To illustrate this point, she presented the case of a 61-year-old man with a new diagnosis of GCA. He had experienced constitutional symptoms for five weeks, jaw claudication and new-onset fronto-temporal headache. Inflammatory markers were elevated and ultrasound demonstrated bilateral halo sign of the temporal arteries. His symptoms and inflammatory markers improved when he was taking 40 mg of prednisone; however, his symptoms returned upon tapering to 30 mg. He underwent temporal artery biopsy which was negative. Upon referral to the NIH for a second opinion, urinalysis demonstrated red blood cell casts and serologic testing demonstrated positive anti-myeloperoxidase antibodies. He underwent kidney biopsy and was diagnosed with ANCA-associated vasculitis with pauci-immune glomerulonephritis.

Dr. Kermani outlined a framework for assessing GCA on the basis of low, intermediate and high pre-test probability, pointing out that ultrasound is most useful on both extremes of the spectrum: a negative study in a low-probability patient or a positive study in a high-probability patient.12 In instances with greater uncertainty or discordant findings, temporal artery biopsy can serve as the decisive test. 

She pointed out that the data for use of ultrasound in GCA originate from expert centers, but many GCA cases are diagnosed by internists or in non-expert centers. “Yes, if you’re Wolfgang Schmidt doing an ultrasound, you don’t need a biopsy, but what about the rest of us? Expertise should dictate your diagnostic approach.”

Dr. Tenaz provided important recommendations to increase the yield of temporal artery biopsy: they should be 2–3 cm in length, obtained in a timely manner and reviewed directly with the pathologist. Red flags suggestive of an alternative diagnosis include lack of granulomatous inflammation, as well as the presence of fibrinoid necrosis or eosinophils. To close, she noted that evaluation for GCA usually involves more than one diagnostic modality and that rheumatologists should be familiar with them all.

Q&A & Closing Thoughts

During the Q&A section, one attendee expressed concern that temporal artery ultrasound is often performed by technicians without standardized protocols and subsequently read by radiologists without expertise in GCA. Dr. Schmidt whole-heartedly agreed, and recommended that rheumatologists spearhead training efforts and establish protocols for vascular imaging. Another attendee also commented on the challenges of obtaining expertise in performing temporal artery ultrasound in the U.S., arguing the debate itself is somewhat artificial and the preference for one study over another is largely based on regional expertise.

In summary, ultrasound is becoming an increasingly important and highly practical tool for the diagnosis of GCA; however, its implementation is limited by a requirement for technical expertise in performing and interpreting the scans. Likewise, due to the risk of false positive ultrasounds and cases of intermediate pre-test probability, biopsy and other imaging modalities remain important tools in the rheumatologist’s diagnostic armamentarium.

Michael Cammarata, MD, RhMSUS, is an assistant professor of medicine at the Johns Hopkins University School of Medicine, Baltimore.

References

  1. Maz M, Chung SA, Abril A, et al. 2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Giant Cell Arteritis and Takayasu Arteritis. Arthritis Rheumatol. 2021 Aug;73(8):1349–1365. 
  2. Dejaco C, Ramiro S, Bond M, et al. EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice: 2023 update. Ann Rheum Dis. 2024 May 15;83(6):741–751.
  3. Ponte C, Grayson PC, Robson JC, et al. 2022 American College of Rheumatology/EULAR classification criteria for giant cell arteritis. Ann Rheum Dis. 2022 Dec;81(12):1647–1653. 
  4. Bowling K, Rait J, Atkinson J, Srinivas G. Temporal artery biopsy in the diagnosis of giant cell arteritis: Does the end justify the means? Ann Med Surg (Lond). 2017 Jun 15;20:1–5.
  5. Schmidt WA, Kraft HE, Vorpahl K, Völker L, Gromnica-Ihle EJ. Color duplex ultrasonography in the diagnosis of temporal arteritis. N Engl J Med. 1997 Nov 6;337(19):1336–1342.
  6. Schmidt WA. Vascular ultrasound in rheumatology practice. Best Pract Res Clin Rheumatol. 2023 Mar;37(1):101847.
  7. Molina-Collada J, Castrejón I, Rivera J, et al. The role of ultrasound and FDG-PET/CT to detect extracranial artery involvement in patients with suspected large vessel vasculitis. Mod Rheumatol. 2023 Apr 13;33(3):549–556. 
  8. Dejaco C, Ponte C, Monti S, et al. The provisional OMERACT ultrasonography score for giant cell arteritis. Ann Rheum Dis. 2023 Apr;82(4):556–564.
  9. Monti S, Ponte C, Schäfer VS, et al. The giant cell arteritis (GCA) ultrasound score (OGUS) at diagnosis and after initial treatment predicts future relapses in GCA patients: Results of a multicentre prospective study. Ann Rheum Dis. 2025 May;84(5):823–832.
  10. Patil P, Williams M, Maw WW, et al. Fast track pathway reduces sight loss in giant cell arteritis: results of a longitudinal observational cohort study. Clin Exp Rheumatol. 2015 Mar–Apr;33(2 Suppl 89):S103–S106.
  11. Schmidt WA, Czihal M, Gernert M, et al. Recommendations for defining giant cell arteritis fast-track clinics. English version. Empfehlungen zur Definition von Riesenzellarteriitis-Fast-Track-Kliniken. Z Rheumatol. 2024 Dec;83(Suppl 3):285–288.
  12. Mackie SL, Dejaco C, Appenzeller S, et al. British Society for Rheumatology guideline on diagnosis and treatment of giant cell arteritis: executive summary. Rheumatology (Oxford). 2020 Mar 1;59(3):487–494.
  13. Schmidt WA, Schäfer VS. Diagnosing vasculitis with ultrasound: Findings and pitfalls. Ther Adv Musculoskelet Dis. 2024 Jun 5;16:1759720X241251742.