Value of 18F-FDG-PET/CT in patients with fever of unknown origin and unexplained prolonged inflammatory syndrome: a single centre analysis experience

Summary Objective: The aim of our study was to evaluate the diagnostic contribution of 18F-fluoro-deoxyglucose (18F-FDG)-positron emission tomography (PET)/computed tomography (CT) in patients with fever of unknown origin (FUO) or unexplained prolonged inflammatory syndrome (UPIS) in real life. Patients and methods: We performed a retrospective study including 14 patients with FUO or UPIS hospitalised in our institution (Strasbourg University Hospital, France) between January 2005 and July 2006. 18F-FDG-PET/CT was considered helpful when abnormal results allowed an accurate diagnosis. Results: 18F-FDG-PET/CT was helpful in half the patients (7/14) for final diagnosis. A diagnosis was reached in 87.5% of the patients (7/8) with an abnormal 18F-FDG-PET/CT but only in 50% of the patients (3/6) with a normal 18F-FDG-PET/CT. Conventional chest and abdominal CT was performed in 13 patients before ordering 18F-FDG-PET/CT. We considered that 18F-FDG-PET/CT was essential to establish the final diagnosis in only 23% of the patients (3/13) since neither chest nor abdominal CT identified abnormalities consistent with the final diagnosis. However, among the three patients, two were diagnosed with large vessel vasculitis and one patient with local prosthetic infection. Conclusions: Our study supports the potential interest of 18F-FDG-PET/CT in the diagnostic workup of FUO and UPIS as it helped establish a fine diagnosis in half of the cases. However, 18F-FDG-PET/CT appeared to be essential to the final diagnosis in only 23% of the cases. In our opinion, this protocol should be performed as a second level test, especially when conventional CT is normal or is unable to discriminate between active and silent lesions.