To further understand the etiological distribution of fever of unknown origin (FUO) in patients underwent ¹⁸F-fluorodeoxyglucose (FDG) PET/CT imaging, and to explore the significance of ¹⁸F-FDG PET/CT in the diagnosis of different types of diseases in FUO patients.

From January 2013 to August 2019, the clinical and PET/CT image data of 466 FUO patients (194 males, 272 females, age: 3-91(52.7±20.9) years) in Peking University People′s Hospital were retrospectively analyzed. The etiological distribution of FUO patients was analyzed according to the final clinical diagnosis. PET/CT imaging manifestations were analyzed for different types of diseases in FUO patients. The role of ¹⁸F-FDG PET/CT in differential diagnosis for FUO was evaluated through clinical questionnaire. Data were analyzed by using χ² test.

The common disease types in FUO patients were rheumatic and immune disease (48.7%, 227/466), infection (28.5%, 133/466) and malignant tumor (11.2%, 52/466). For PET/CT imaging, 95.5% (445/466) of the patients were positive, of which 313 (70.3%, 313/445) were found to have focal lesions, and the other 132 (29.7%, 132/445) showed only nonspecific abnormal uptake. Lesions in different types of diseases were varied in the location, morphological changes as well as FDG uptake. The results of the questionnaire showed that PET/CT imaging could benefit 95.9% (447/466) of the patients in the FUO diagnosis and treatment. PET/CT reached direct etiological diagnosis of malignant tumors more frequently than other types of diseases (χ² values: 14.408-25.466, all P<0.001). PET/CT helped or directly reached the etiological diagnosis of rheumatologic diseases more frequently than infection and unknown cause group(χ² values: 7.922, 9.647, both P<0.05).

¹⁸F-FDG PET/CT imaging has high clinical value in the diagnosis of FUO etiology and can provide multilevel diagnostic information.

Fever; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose