The role of ultrasound and FDG-PET/CT to detect extracranial artery involvement in patients with suspected large vessel vasculitis

Objective To assess the accuracy of ultrasound (US) versus fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) to identify extracranial involvement in large vessel vasculitis (LVV). Methods A retrospective observational study of patients with suspected LVV. All patients underwent US exam within 24 h per protocol. FDG-PET/CT was performed according to clinician criteria. The gold standard for LVV diagnosis was clinical confirmation after 6 months. Results Of the 113 patients included (74.3% female, mean age 74 years), 37 (32.7%) were diagnosed with LVV after 6 months. The sensitivity and specificity of US were 86.5% and 96.1%, respectively. Only 12 (42.9%) of 28 patients undergoing a FDG-PET/CT per clinician criteria showed positive findings. The sensitivity and specificity of FDG-PET/CT for LVV were 61.1% and 90%, respectively. Taking FDG-PET/CT as the reference, US showed extracranial inflammation in 10/12 (83.3%) and detected 2 (12.5%) additional cases of extracranial involvement with negative FDG-PET/CT. Conversely, FDG-PET/CT was positive in two patients with negative US (one isolated aortitis and one aortoiliac involvement). Conclusions US and FDG-PET/CT are both valid tools to detect extracranial involvement. The presence of US extracranial artery inflammation is consistent with FDG-PET/CT examination, although a negative US scan does not rule out extracranial involvement.