Temporal artery biopsy has been the standard for diagnosing giant cell arteritis (GCA), but vascular ultrasound, a procedure that's less invasive, less time-intensive, less expensive, and more convenient, has gained widespread use in Europe, and now clinics in the United States are adopting this approach and moving toward having rheumatologists take on the role of ultrasonographer.
However, directors at these clinics — known as GCA fast-track clinics — caution that the bar can be high for adopting vascular ultrasound (VUS) as a tool to diagnose GCA. Ultrasonographers need specialized training to perform the task and an adequate caseload to maintain their skills. Clinics also need to be outfitted with high-definition US machines.
"It definitely takes adequate training and learning of how to adjust the settings on the ultrasound machine to be able to visualize the findings appropriately," said Minna Kohler, MD, director of the rheumatology and musculoskeletal ultrasound program at Massachusetts General Hospital in Boston, which has its own GCA fast-track clinic.
"And the clinical context is very important," she said. "If you have a high suspicion for someone with temporal arteritis, or GCA, and the patient has been on steroids for weeks before you see them, the ultrasound findings may not show signs of the disease. In those cases in which the imaging is equivocal, we would still pursue a biopsy."
The idea of the fast-track clinic is as the name implies: to quickly confirm the presence of GCA in a matter of hours, or days at the most, in an outpatient setting without the hassles of a biopsy. Temporal artery biopsy (TAB), by comparison, "is more costly because it requires operating room time, a surgical consultation, and surgery time, whereas ultrasound is a very inexpensive exam since it's done in the clinic by the rheumatologist," Kohler said.
Use of VUS to diagnose GCA is supplanting TAB in Europe and other countries. In Denmark alone — with a population of 6 million — three outpatient fast-track clinics are operating. The United States, with a population more than 50 times larger than Denmark's, has six.
Stavros Chrysidis, MD, PhD, chief of rheumatology at the Hospital South West Jutland, one of the fast-track clinic sites in Denmark, led a recent multicenter study, known as EUREKA, of VUS in patients with suspected GCA. He and his colleagues reported in The Lancet Rheumatology that the sensitivity and specificity of VUS was superior to TAB in confirming a diagnosis of GCA. Chrysidis has instructed US rheumatologists and ultrasonographers in performing and interpreting VUS for GCA.
The study emphasizes the importance of training for ultrasonographers, said Chrysidis, who regularly performs VUS at his institution. "The most important finding is that when we apply VUS by systematically trained ultrasonographers using appropriate equipment in appropriate settings, it has excellent diagnostic accuracy on GCA," he told Medscape Medical News.
He noted that The Lancet Rheumatology report is the first multicenter study of VUS for diagnosing GCA in which all the ultrasonographers participated in a standardized training program, which his group developed. "Ultrasound is very operator dependent," he said. "That's why the training is very important."
The training occurred over a year and included two workshops consisting of 5 days of theoretical training on VUS; supervised hands-on evaluation of healthy individuals and patients with known GCA; and evaluation of US images. Over the course of the year, trainees performed at least 50 VUS evaluations, half of which were in patients with confirmed GCA. During the training period, an external rheumatologist with broad experience in VUS made the final diagnosis.
"The equipment and settings are very important because ultrasound can be very time-consuming if you are not educated well and if your equipment is not adjusted well," Chrysidis said. The equipment must be calibrated beforehand "so you don't spend time on adjustments."
For diagnosing temporal artery anomalies, the ultrasound equipment must have a resolution of 0.3 - 0.4 mm, he said. "When you have a transducer of 10 MHz, you cannot visualize changes smaller than 5 mm."
The EUREKA study stated that VUS could replace TAB as a first-line diagnostic tool for GCA — provided the ultrasonographers are systematically trained and the equipment and settings are appropriate. In the Jutland clinic, VUS already has replaced TAB, Chrysidis said.
"In my department since 2017, when we started the fast-track clinic after the EUREKA study was terminated, we have performed three temporal artery biopsies in the last 4 years, and we screen 60-70 patients per year because we use ultrasound as the primary imaging," he said. In cases when the results are inconclusive, they order a PET scan. "We don't perform biopsies anymore," he said.
US Fast-Track Clinic Models
The fast-track clinic models in the United States vary. Results of a survey of the US clinics were presented as an abstract at the 2021 American College of Rheumatology Annual Meeting. Some centers have a vasculitis specialist obtain and interpret the imaging. At others, a vasculitis specialist refers patients to a VUS-trained rheumatologist to perform and interpret the test. Another approach is to have vasculitis specialists refer patients to ultrasound technicians trained in VUS, with a vascular surgeon interpreting the images and either a VUS-trained rheumatologist or vascular medicine specialist verifying the images.
The take-home message of that survey is that "ultrasound evaluation should be considered in the hands of experts, realizing that not everyone has that skill set, but if it is available, it's a way to expedite diagnosis and it can be helpful in managing the GCA patient in an appropriate way, quicker than trying to schedule cross-sectional imaging," said Mass General's Kohler, who is a co-author of the abstract. "Certainly, cross-sectional imaging also plays an important role, but when it comes to confirming whether to continue with treatment or not for a very serious condition, ultrasound is a quick way to get the answer."
In addition to the fast-track clinic at Mass General, the survey included fast-track clinics at the University of Washington in Seattle; Brigham and Women's Hospital in Boston; Loma Linda University in Loma Linda, California; UCLA in Los Angeles; and at a private practice, Arthritis and Rheumatism Associates in the Washington, DC area.
Advantages of VUS vs TAB
At Mass General, some of the rheumatologists are trained to perform VUS. The rheumatologists also perform the clinical evaluation of suspected cases of GCA. The advantage of VUS, Kohler said, is that the answer is "right there"; that is, the imaging yields a diagnosis almost instantaneously whereas a biopsy must be sent to a lab for analysis.
"Since a lot of patients with suspected vasculitis may already come to us on steroid therapy, and if there's a low probability or low suspicion for vasculitis, [VUS] actually confirms that and we're able to taper prednisone or steroids quickly rather than keep them on a prolonged course."
Alison Bays, MD, MPH, assistant professor of rheumatology at the University of Washington, said that the advantages of avoiding biopsy aren't to be overlooked. "Temporal artery biopsies are invasive and carry surgical risks, especially as many of our patients are elderly," she told Medscape Medical News.
"These patients occasionally refuse biopsy, but the acceptance of ultrasound is high," Bays said. "Scheduling surgery can be more complicated, resulting in delays to biopsy and potentially higher rates of false negatives. Additionally, ultrasound has resulted in a higher rate of diagnosis with GCA as TAB misses large-vessel involvement." The fast-track clinic there has evaluated 250 patients since it opened in 2017.
Bays and colleagues published the first United States study of a fast-track protocol using vascular sonographers. "Our group has demonstrated that fast-track clinics can rapidly and effectively evaluate patients, and we demonstrated a different method of evaluation using vascular sonographers rather than rheumatologists to do the vascular ultrasound," she said. "It utilizes the familiarity vascular sonographers already have with imaging blood vessels."
She added that the TABUL study in the United Kingdom in 2016 demonstrated that VUS yielded a savings of $686 (£484 as reported in the study), compared with TAB. "Further studies need to be done in the United States," she said. "Beyond direct comparison of costs, reduction in steroid burden due to quick evaluation and diagnosis may carry additional benefits."
At Brigham and Women's Hospital, the division of rheumatology and the vascular section of the cardiology division collaborate on the GCA evaluation, said Sara Tedeschi, MD, MPH, co-director of the fast-track clinic there. Trained vascular technologists credentialed in the procedure and specifically trained in using VUS for evaluating arteritis perform the VUS. Cardiologists with a subspecialty in vascular medicine interpret the studies.
VUS patients have a rheumatology evaluation just before they have the ultrasound. "The rheumatology evaluation is then able to incorporate information from the VUS together with laboratory data, the patient's history, and physical examination," Tedeschi said.
"If the rheumatologist recommends a temporal artery biopsy as a next step, we arrange this with vascular surgery," she said. "If the rheumatologist recommends other imaging such as MRA [magnetic resonance angiography] or PET-CT, we frequently review the images together with our colleagues in cardiovascular radiology and/or nuclear medicine."
But in the United States, it will take some time for GCA fast-track clinics to become the standard, Tedeschi said. "Temporal artery biopsy may be faster to arrange in certain practice settings if VUS is not already being employed for giant cell arteritis evaluation," she said.
Bays recognized this limitation, saying, "We are hoping that in the future, the American College of Rheumatology will consider vascular ultrasound as a first-line diagnostic test in diagnosis as rheumatologists and vascular sonographers gain familiarity over time."
But that would mean that centers performing VUS for GCA would have to meet rigorous standards for the procedure. "With that, standardization of a protocol, high-quality equipment, and adequate training are necessary to ensure quality and reduce the chance of false-positive or false-negative results," she said.
Chrysidis, Bays, and Tedeschi have disclosed no relevant financial relationships. Kohler is a board member of Ultrasound School of North American Rheumatologists.
Richard Mark Kirkner is a Philadelphia area-based healthcare journalist.
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Lead Image: Brigham and Women’s Hospital
Image 1: Massachusetts General Hospital/Harvard Medical School
Image 2: Hospital of Southwest Jutland, Denmark
Image 3: Brigham and Women's Hospital
Image 4: University of Washington
Image 5: Brigham and Women’s Hospital
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Cite this: Giant Cell Arteritis Fast-Track Clinics Pave Way for Greater Ultrasound Use in US - Medscape - Dec 07, 2021.