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.
Brigham and Women's Hospital
Magda Abdou, a senior vascular technologist at Brigham and Women’s Hospital vascular diagnostic lab, performs an ultrasound evaluation of the temporal artery.
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 ultrasound 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.
Dr. Minna Kohler
“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,” Dr. Kohler said.
European experience
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.
Dr. Stavros Chrysidis
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. Dr. Chrysidis has instructed U.S. rheumatologists and ultrasonographers in performing and interpreting VUS for GCA.
The study emphasizes the importance of training for ultrasonographers, said Dr. 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 this news organization.
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 ultrasound 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,” Dr. 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, Dr. 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.