Role of 18 F-FDG PET-CT in Vasculitis: A Prospective Study

Objective: Evaluate the diagnostic accuracy of PET in patients with fever of unknown origin (FUO) and in patients with suspected and/or proved large vessel vasculitis (LVV). Patients and methods: 72 patients (49 females, 23 males; mean age 63 y, range 23-82) were prospectively examined with PET between February 2010 and April 2013; 42 with suspected LVV, 15 with LVV during steroid therapy, and 15 with fever of unknown origin (FUO). Follow-up scans were performed in 19 patients. A semi-quantitative analysis [Vessel SUVmax]/[liver SUVmax] was performed to rate the disease in a 4-step system. PET scans were compared with temporal artery biopsy and MRI and/or angio-CT of a specific region. Results: Pathological 18 F-FDG (FDG) uptake was observed in 30/72 (42%) patients, and negative in 42/72 (58%) patients. In 42 patients with suspected LVV 9 (21%) were positive, and 33 (79%) negative; 11 (73%) of the 15 steroid-treated patients with LVV were positive, and 4 (27%) negative; 10 (67%) of the 15 patients with FUO were positive and 5 (33%) negative. PET had an overall sensitivity of 87% [95% confidence interval (CI) 79-95%], a specificity of 95% (95% CI 90-100%), a positive predictive value of 93% (95% CI 87-99%) and a negative predictive value of 91% (95% CI 84-97%). The diagnostic accuracy of PET was 92% (95% CI 85-98%). Conclusions: 18 F-FDG PET/CT especially that based on semi quantitative analysis is a sensitive and specific imaging tool for the diagnosis of LVV but also for therapy monitoring and follow up.