Giant cell arteritis in sight - Imaging techniques in the ZGT GET cohort

Giant cell arteritis (GCA) is a large vessel vasculitis with potentially
devastating complications that can be prevented when treatment is started as
soon as possible. The affected population is older than 50 years with a
peakincidence above 70 years. It is a rare disease with an incidence of 1 in
10000 personyears. The typical presentation is a new onset headache, mostly
temporally located, jaw claudication and certain visual symptoms combined with
pain over the temporal artery, decreased pulsations and elevated inflammatory
markers. Less known is the presentation with symptoms such as fever and weight
loss. Visual loss, cerebrovascular accidents and aneurysms of the aorta are the
potential complications of GCA. These complications can be prevented by a
timely treatment with corticosteroids. Unfortunately, corticosteroids have many
side effects leading to a significant impact of the disease even when treated
adequately. So, there is a need for an early and accurate diagnosis, which is
difficult with the current standard of care. The elevated inflammatory markers
(ESR and CRP) are aspecific, and a biopsy of the temporal artery is not very
sensitive as well as invasive and with a delayed result. Until now the biopsy
is regarded the golden standard due to a lack of a better test. Meanwhile,
non-invasive imaging techniques are emerging, such as ultrasound sonography,
MRI/MRA and FDG-PET/CT. These are quick and may aid during the course of GCA.
Compared to the biopsy, recent literature has shown some promising results for
these techniques. However, due to a lack of a direct comparison between the
three techniques the question remains which one is best to diagnose GCA.

To aid early diagnosis of GCA, the current research project was initiated in a
collaboration between the Ziekenhuisgroep Twente (ZGT) and the University
Twente (UT).

The overall aim is to improve therapy and prognosis in patients with GCA by
improving the diagnostic process. We wish to do so by comparing 3 imaging
techniques in a cross-sectional manner. The following goal was formulated:

To compare validity and accuracy of ultrasound sonography, FDG-PET/CT and
MRI/MRA with each other in comparison to the reference standard for the study;
the diagnosis of the rheumatologist after 6 months.

Nested-case control study within a cohort (ZGT GET cohort)

Two imaging techniques (FDG-PET/CT and MRI/MRA) will be performed in addition
to ultrasound sonography as ultrasound sonography is already a part of our
usual care at baseline. Both FDG-PET/CT and MRI/MRA are used often in the usual
care of other diseases. As information flyers are available for both FDG-PET/CT
and MRI/MRA from usual care, patients in our study will also receive these
flyers in addition to the study information. Contraindications for both imaging
techniques will be applied. If these are used, the risks of both imaging
techniques are negligible. Ultrasound sonography is harmless. For FDG-PET/CT
and MRI/MRA certain agents are used, but these hardly have side effects.
Furthermore, the radiation load is low - about 4,5 mSv - and not harmful for
the patient or his or her environment. No iodine agents will be used and a low
dose CT will be done.
We therefor do not expect any additional risks with this study, however, there
is a significant time burden on patients. The FDG-PET/CT procedure can take up
to 3 hours and a MRI/MRA 30-45 minutes. For both an intravenous line is
necessary. Unfortunately there is no other way to address this research
question. A RCT or cohort comparing these imaging techniques by comparing
(similar) patients groups is not possible due to the need for large patient
populations for these types of studies. As GCA is a rare disease these patient
populations are not possible. Nonetheless, there is a need to compare these
imaging techniques to better use imaging techniques in the diagnosis of GCA in
the future. Perhaps the current study may even contribute to the reduction of
temporal artery biopsies for the diagnosis of GCA.