Fever of unknown origin: The role of 18F-FDG PET/CT

Abstract

Fever of unknown origin (FUO) is a challenging diagnostic problem. Timely identification and precise localization of the causing process are critical for appropriate patient management. The present prospective study evaluates the role of PET/CT using 18F-FDG in the investigation of FUO. Methods: A total of 48 consecutive patients (25 men, 23 women; age range, 24-82 y) with FUO underwent 18F-FDG PET/CT scans. FUO was defined as a fever of more than 38.3°C that lasted for more than 3 wk and failure to reach diagnosis after more than 1wk of inpatient investigation. The performance of PET/CT for identifying the etiology of FUO was assessed. Final diagnosis was based on histopathology, microbiologic assays, or clinical and imaging follow-up. Results: PET/CT detected suggestive foci of increased 18F-FDG uptake in 27 patients. In 22 of these 27 positive studies (81%), PET/CT identified the underlying disease and diagnosed infection in 9 patients, an inflammatory process in 10 patients, and malignancy in 3 patients. 18F-FDG PET/CT was negative in 21 patients. All these patients were diagnosed as having systemic nonfocal infection or drug-induced fever or showed spontaneous resolution of the febrile statewith no further evidence of a localized inflammatory, infectious, ormalignant process for a clinical follow-up period of 12-36 mo. Conclusion: 18F-FDG PET/CT identified the underlying cause of the fever in 46% of the present study population and contributed to the diagnosis or exclusion of a focal pathologic etiology of the febrile state in 90% of patients. 18F-FDGPET/CT has a high negative predictive value (100%) for assessment of FUO. If confirmed by further studies, 18F-FDG PET/CT may be used in the future as an initial noninvasive diagnostic modality for assessment of this group of patients. Copyright © 2008 by the Society of Nuclear Medicine, Inc.