First EULAR Guidance on Imaging in Large Vessel Vasculitis

Janis C. Kelly

February 01, 2018

New recommendations from the European Union League Against Rheumatism (EULAR) address the use of imaging in large vessel vasculitis (LVV) such as giant cell arteritis (GCA) and Takayasu arteritis (TAK). Imaging has become common in the diagnosis and management of primary LVV; however, clear standards on how it should be used are lacking.

A EULAR working group led by Christian Dejaco, MD, from the Department of Rheumatology and Immunology, Medical University Graz, Austria, published the recommendations online January 22 in the Annals of the Rheumatic Diseases.

A key change from earlier standard practice is the recommendation for early imaging in patients with suspected LVV; specifically, ultrasound in suspected GCA and magnetic resonance imaging (MRI) in suspected Takayasu arteritis. The authors recommend temporal artery biopsy (TAB) if the diagnosis is still uncertain after imaging. They also recommend imaging in cases of suspected flare. A major reason for pushing early imaging is that "ultrasound-guided fast-track strategies have led to a reduction of irreversible vision loss, and the concept of imaging confirmed large vessel (LV-)GCA with or without cranial disease, has been added to the disease definition," the authors explain.

Dr Dejaco told Medscape Medical News, "Knowledge in the field of imaging, particularly ultrasound, has steadily increased, and imaging is now used more and more as a primary diagnostic test in clinical practice. However, there has still been significant uncertainty about the value of these techniques, and it has still been unclear which method should be applied in which situation. Besides, new therapies have become available for the treatment of GCA, and therefore, the question of the possible value of imaging for monitoring purposes has been raised."

The authors conducted a systematic literature review on imaging methods including ultrasound, MRI, computed tomography, and [18F]-fluorodeoxyglucose positron emission tomography (PET) used in LVV. The task force, which included 20 physicians, healthcare professionals, and patients from 10 EULAR countries, then developed 12 recommendations to guide clinical practice.

Dr Dejaco explained that these are the first recommendations to specifically address the role of imaging for diagnosis and monitoring of LVV in clinical practice. "Previous recommendations considered imaging, and particularly ultrasound, as a tool for further research. The current recommendations suggest using imaging in first place, assuming that it is readily available and conducted with high expertise," he said.

However, Dr Dejaco warned that this recommendation should not be taken as advice against performing TAB in GCA. "In settings where imaging modalities are not readily available or expertise with imaging is questionable, a biopsy should still be favored. Where imaging and TAB are readily available and performed with high quality, imaging should be preferred as the first test because of low invasiveness, ready availability of imaging results, and assessment of a larger extent of potentially inflamed arteries at the same examination, thus contributing to a lower number of false-negative results," he explained.

The task force recommends MRI as a first imaging test for TAK. Conventional angiography, which has long been the gold standard for the diagnosis of TAK, is not recommended except as part of a vascular intervention such as percutaneous transluminal balloon angioplasty or stenting. "Biopsy of temporal arteries in TAK is frequently negative, and histology of large extracranial vessel is usually not possible," Dr Dejaco added.

Philip Seo, MD, associate professor of medicine and director, Johns Hopkins Vasculitis Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, told Medscape Medical News, "The 12 recommendations seem reasonable to me. They really highlight the limits of the physical examination in the assessment of patients with [LVV] and give some general guidance as to which modalities might be the most useful in a given scenario. The recommendations highlight how much we still do not know about the use of imaging for the ongoing assessment of patients who have an established diagnosis of [LVV]." Dr Seo was not involved in the task force.

Community Radiologists in United States May Lack Expertise in Imaging for LVV

Dr Seo said all the imaging modalities included in the EULAR recommendations are available in the United States, but the required expertise may not be.

"Ultrasound in particular is a very useful modality in the hands of an experienced practitioner, but that level of experience in vascular ultrasound just is not widely available in the United States. Even with modalities like MRI and [computed tomography], I wonder how many community radiologists see vasculitis frequently enough that they can interpret these studies with confidence. This is the biggest hurdle to the implementation of these recommendations in the United States," Dr Seo explained.

Abhijeet Danve MD, RhMSUS, FACP, assistant clinical professor, Yale School of Medicine, Yale New Haven Hospital, Connecticut, agreed with Dr Seo.

Dr Danve, who was not involved in the EULAR task force, told Medscape Medical News, "Dejaco et al recommend that ultrasound of temporal arteries can substitute the temporal artery biopsy, which seems controversial especially in [the United States], where only a limited number of rheumatologists perform this type of ultrasound. This is an operator-dependent technique that can have interreader variability. I agree that it can definitely help to predict pretest probability before biopsy and complement the biopsy, but I still feel that TAB is the gold standard test unless a more objective and feasible imaging test becomes available."

He also noted that high-resolution MRI of cranial arteries is not routinely performed even in tertiary care institutions, and that rheumatologists across the United States are not routinely ordering this test.

"It is very difficult to get PET scan approved by most insurance companies in [the United States] for the purpose of diagnostic imaging for suspected large vessel vasculitis, even though the PET scan is clearly very useful for diagnosis of noncranial GCA and also helps to exclude other systemic illnesses such as infections and malignancies. This is a practical issue faced by most rheumatologists," he added.

For routine community clinical practice, Dr Dejaco said, "An early imaging test should be performed (if readily available and conducted with high expertise) to complement the clinical criteria for diagnosing GCA. However, waiting for imaging should not delay therapy in case of a high suspicion of GCA because of the imminent threat of blindness. A positive ultrasound result can often be detected up to 1 week after start of treatment. If imaging is not available or expertise is questionable, TAB is still the preferred test."

Dr Dejaco also emphasized interpreting imaging results against the background of pretest clinical probability. "If there is a high clinical probability and a positive imaging result, the diagnosis of GCA can be accepted without further testing. In patients with a low clinical probability and a negative imaging result, the diagnosis of GCA can be considered unlikely, whereas in all other situations, additional efforts towards a diagnosis are necessary," he explained.

Dr Dejaco said that two major unmet needs are for a consensus statement about the best imaging modality to monitor the development of aneurysm in patients with GCA and for a standardized quantitative technique for reading the FDG-PET, to replace current semiquantitative methods.

Questions also remain about the value of imaging techniques, particularly MRI, computed tomography, and PET, in extracranial LVV. "Although these techniques are frequently used, particularly in patients with fever of unknown origin, polymyalgia, and constitutional symptoms to detect possible underlying LVV, there are few prospective studies evaluating the sensitivity and specificity of these techniques for extracranial LVV," Dr Dejaco said.

"The value of imaging for monitoring purposes, as well as its role as a prognostic factor, are elusive so far. Whether tracer accumulation in large vessels in PET studies of patients in remission indicates inflammation or remodeling is unclear, as is the prognostic significance of tracer uptake at the aorta for the future development of aortic aneurysms," he explained.

The study was funded by EULAR. Dr Dejaco, Dr Seo, and Dr Danve have disclosed no relevant financial relationships.

Ann Rheum Dis. Published online January 22, 2018. Full text

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