Impact of ultrasound limitation to assess aortitis in patients with giant cell arteritis: comparative study with FDG-PET/CT.

Objective: To determine the impact of ultrasound (US) intrinsic limitation to assess aortitis versus FDG-PET/CT in patients with US-proven giant cell arteritis (GCA) and to identify factors associated with aortic involvement.

Methods: Retrospective observational study of patients referred to US fast-track clinics at two academic centres over a 4-year period. Only patients with GCA confirmed by US were included. Temporal arteries (TA) and extracranial arteries US were performed at baseline. FDG-PET/CT was performed according to clinician's criteria. An FDG artery uptake at the aorta higher than liver uptake was considered positive for aortitis.

Results: Seventy-two of 186 patients with US-proven GCA underwent an FDG-PET/CT; 29 (40.3%) had a positive FDG-PET/CT and 24 (33.3%) presented aortitis. Only 6 (20.7%) patients with positive FDG-PET/CT had negative US findings of large vessel (LV)-GCA. Among patients with aortitis in FDG-PET/CT, only two (8.3%) had negative US findings of LV-GCA. Patients with aortitis were younger (68.9 vs 81;p<0.001), more frequently females (79.2% vs 39.6%;p=0.002) and had higher platelets count (413.4 vs 311.1;p=0014). Patients with aortitis presented positive TA US less frequently (41.7% vs 83.3%;p<0.001), but more LV US involvement (91.7% vs 41.7%; p<0.001) versus patients without aortitis. None of the patients with aortitis exhibited visual symptoms (0% vs 31.2%;p=0.001).

Conclusions: FDG-PET/CT can detect aortitis in one out of every three patients with US-proven GCA. However, a negative US examination for LV-GCA suggests a low risk of aortitis. Younger and female GCA patients with thrombocytosis, absence of visual manifestations and LV-GCA on US may more frequently present aortitis by FDG-PET/CT.