[Usefulness of (18)FDG PET-CT scan as a diagnostic tool of fever of unknown origin]

Classic fever of unknown origin (FUO) is defined as the presence of fever greater than 38.3°C of at least 3 weeks with an uncertain diagnosis. Identification of the etiology is crucial in guiding further diagnostic procedures and subsequent patient management. The aim of this study was to evaluate the role of fluorine-18 fluorodeoxyglucose ((18)F-FDG) positron emission tomography combined with computed tomography (PET/CT) in the diagnostic orientation of FUO.

An observational retrospective study was performed, including 30 consecutive patients who had been studied between March 2010 and September 2013. Twenty-six out of 30 patients (86.67%) had a definitive diagnosis after pathologic confirmation in 15 cases, microbiological findings in one patient and clinical and radiological follow-up in 10 patients (mean: 16.38 months).

Among the positive scans, malignancy (n=10), inflammatory (n=8), infectious (n=4) and miscellaneous causes (n=1) were identified. (18)F-FDG PET/CT had a diagnostic accuracy of 90.00%, sensitivity of 88.46% (95% confidence interval [95% CI] 76-101), specificity of 100.00% (95% CI 100-100), positive predictive values of 100.00% (95% CI100-100) and negative predictive value of 57.14% (95% CI 20-91).

(18)F-FDG PET/CT provided useful for the etiologic diagnosis of FUO, with high sensitivity and specificity. (18)F-FDG PET/CT has an incremental morphological and functional value, especially indicating the best biopsy site.