The Efficacy of 18F-FDG PET/CT and 67Ga SPECT/CT in Diagnosing Fever of Unknown Origin

Abstract Objective Fever of unknown origin (FUO) is a diagnostic challenge. This study aimed to assess the efficacy of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET/CT) and gallium-67 single-photon emission computed tomography/computed tomography ( 67 Ga SPECT/CT) in diagnosing FUO. Methods A total of 68 patients with FUO underwent 18 F-FDG PET/CT and 67 Ga SPECT/CT from January 2013 through May 2016. Images were read independently. The imaging results were compared with the final diagnosis and categorized as helpful for diagnosis or non-contributory to diagnosis in the clinical setting. Associations between categorical variables were evaluated with the chi-square test or Fisher's exact test. Results Ten of the 68 patients were excluded. An infectious underlying disease was found in 23 patients. A malignant disorder was the cause of FUO in 10 patients. Non-infectious inflammatory disease was found in 11 patients. Adrenal insufficiency was the cause of FUO in two patients. The cause of FUO was not found for 12 patients. A high false-positive rate of 44% (7/16) was observed for 18 F-FDG PET/CT, while a high false-negative rate of 55% (23/42) was observed for 67 Ga SPECT/CT. 18 F-FDG PET/CT studies depicted all 67 Ga-avid lesions. The sensitivity (79% vs. 45%) and clinical contribution (72% vs. 55%) of 18 F-FDG PET/CT in diagnosing FUO were significantly higher than those of 67 Ga SPECT/CT ( p Conclusions On the basis of this study, the diagnostic performance of 18 F-FDG PET/CT is superior to 67 Ga SPECT/CT in the work-up of patients with FUO. With its rapid results and superior sensitivity, 18 F-FDG PET/CT may replace 67 Ga SPECT/CT where this technique is available.