1 Nuklearmedicinsk Afdeling, Aalborg Sygehus, Faculty of Health Sciences, Aarhus University, Aarhus University2 Department of Clinical Medicine, Health, Aarhus University3 Aalborg University Hospital, Dept of Nuclear Medicine, Aalborg, Denmark4 Sheffield University Hospital, Dept of Radiology, Sheffield5 Sheffield University Hospital, Dept of Rheumatology, Sheffield6 unknown7 Department of Clinical Medicine, Health, Aarhus University
Objectives: Fever of unknown origin (FUO) is an increasingly accepted indication for PET/CT where it has a relatively high diagnostic yield. This study assesses its diagnostic value for the revised definition of FUO. Methods: The revised definition of FUO is fever of greater than 38.3C for more than 3 weeks duration and an uncertain diagnosis after comprehensive evaluation as an inpatient or outpatient for a minimum of 3 days or 3 outpatient visits, having excluded immunocompromised states. 59 patients (pts) (F=35, age 18-92) with this definition underwent PET with full diagnostic contrast enhanced CT. The value of PET/CT in determining the underlying etiology of FUO was retrospectively evaluated by comparing the study findings with a final diagnosis. Final diagnosis was formulated by 6 month clinical, imaging, microbiological and histopathological follow up. When no cause was found by follow up, the negative study was considered a true negative. Results: Final diagnosis was made in 35/59 pts. Diagnosis was reached in 86% of these pts with an abnormal study but only in 14% of pts with a normal study. Underlying etiologies included vasculitides (14 pts), infectious foci (14 pts), neoplasm (6 pts) and drug fever (1 pt). Before ordering a PET/CT, conventional CT or MRI was performed in 43 pts. We considered that a PET/CT was essential to establish the final diagnosis in 15/43 pts (35%) with inconclusive CT or MRI. Conclusions: 18F-FDG PET/CT contributed to establishing a final diagnosis in 64% of 47 pts with positive PET/CT findings and in 39% of all pts with the revised definition of FUO.