CHICAGO -- Giant cell arteritis (GCA), a blood vessel inflammation, poses diagnostic issues for patients who need prompt treatment decisions to head off serious complications such as blindness and even death, research presented here suggested.
Researchers from Denmark and Australia presented research at the American College of Rheumatology annual meeting on two diagnostic approaches -- vascular ultrasound and combined positron emission tomography and computed tomography (PET/CT) -- as potential first-line alternatives to biopsies by surgeons. Arterial biopsies have been considered the gold standard.
"A lot of diagnostic testing has been suspect," said Chris Morris, MD, a rheumatologist from Kingsport, Tennessee, and moderator of a press conference where the study results were discussed. "The earlier we can identify the disease, the better it is for a patient to get the right treatment." Treatment is typically a course of corticosteroids.
Role of Ultrasound
Morris said GCA impacts one patient in 50,000 with the majority being older women. A fast-track approach would help patients get needed treatment more quickly, he said: "I've tried to get it done before following a patient on high-dose steroids and I'm told by the surgeon, 'We'll see you sometime next week.' You have a disease that can cause blindness. You don't want to wait. And when you start treatment sometimes that may actually negate the benefit of the biopsy."
Berit Dalsgaard Nielsen, MD, a rheumatologist at the Aarhus University Hospital in Aarhus, Denmark, said cranial GCA patients often present with symptoms such as headache, jaw claudication, and visual disturbances. But she said large vessel GCA rarely displays these symptoms and often presents with constitutional symptoms that mimic infection and cancer.
In addition, biopsies frequently are negative in this group and also biopsies may not be possible.
She noted that some "fast-track" clinics use vascular ultrasound to diagnose GCA, but the techniques accuracy in large-vessel GCA is unknown.
Nielsen's group compared vascular ultrasound and 18FDG-PET/CT.
Research subjects were 50 and older, had C-reactive protein levels of greater than 15 mg/L, had either cranial symptoms, a new onset of claudication of a limb, protracted constitutional symptoms or polymyalgia rheumatica (PMR) symptoms. Patients diagnosed with GCA were used as controls.
Sonographers were blinded to PET results.
Of 86 subjects, 46 were diagnosed with large-vessel GCA with or without cranial GCA. Ten were diagnosed with cranial GCA alone, twenty-one were diagnosed with PMR, and 10 with other diseases.
Thirty-six patients of 45 diagnosed with large-vessel GCA were axillary ultrasound-positive.
"The test had 100% specificity and 80% sensitivity," Nielsen said. "[Vascular ultrasound] actually helped us identify more patients. it may overcome the delay in diagnosis and the patients can be treated earlier."
She concluded that vascular ultrasound "is a reasonable first-line imaging test not only in suspected cranial GCA patients, but in all GCA-suspected patients."
Advanced Imaging
Researchers at Royal North Shore Hospital in Sydney, Australia took a somewhat different slice of the diagnostics comparing PET/CT time-of-flight scans with temporal artery biopsy (TAB) for GCA in patients with suspected disease.
Anthony Sammel, MD, a rheumatologist at Royal North Shore, noted that PET/CT typically has been used to image the aorta and primary arterial branches, but newer technology can also detect inflammation in the smaller temporal, occipital, maxillary, or vertebral arteries.
He noted that patients and doctors lean toward using noninvasive, fast, and lower-risk approaches, such as PET/CT, versus biopsies, which carry risks of bleeding and infection.
The study of 64 patients with suspected GCA patients was conducted over 20 months.
PET/CT was conducted from the vertex to diaphragm within 72 hours of initiating corticosteroid therapy and before TAB.
Two nuclear medicine physicians experienced with PET were blinded to clinical and biopsy data.
They independently reported scans as globally positive or negative for GCA. They also rated the grade that the tracer uptake exceeded the background blood pool for 18 artery segments and the maximum grade per patient.
Grades were 0=none, 1=minimal/equivocal, 2=moderate, and 3=very marked. Discordant results were resolved by consensus among the graders. Clinical diagnosis of GCA was made by consensus at the 6-month mark between the PET/CT-blinded treating physician and blinded external reviewers.
Sammel said a high negative predictive value of 98% indicates this protocol could be used as a first-line test to rule out GCA in suspected patients.
He recommended introduction into clinical care. "The study indicates that a negative scan may be particularly useful in ruling out the disease in patients who have a low pretest probability of GCA," he said.
But are vascular ultrasound and PET/CT ready for prime time?
"I think it depends a bit on the local expertise and the availability [of PET/CT] at this point," Sammel said.
He noted GCA is not "the bread and butter" of all vascular sonographers. "It really requires a sonographer to be able to look at the nature of the plaque or the thickening. I don't think it's as simple as being able to just send [the patient] to any vascular lab for assessment," he said.
Morris, Nielsen, and Sammel agreed that cost is an issue for PET/CT.
Sammel said a PET/CT scan in the United States can cost $5,000, 10 times greater than in Australia. Morris said insurers likely will want patients to undergo the much cheaper ultrasound scan.