Value of Positron Emission Tomography Coupled With Computed Tomography for the Diagnosis of Inflammatory Syndrome of Unknown Origin in an Internal Medicine Department

OBJECTIVE: To evaluate the usefulness of positron emission tomography (PET) coupled with computed tomography (CT) in the diagnostic workup for inflammatory syndrome of undetermined origin (IUO) and to determine the diagnostic delay in an internal medicine department. PATIENTS AND METHODS: We retrospectively studied a cohort of patients for whom a PET/CT scan had been prescribed in an indication of IUO in an internal medicine department (Amiens University Medical Center, Amiens, France) between October 2004 and April 2017. The patients were grouped according to the PET/CT findings: very useful (enabling an immediate diagnosis), useful, not useful, and misleading. RESULTS: We analyzed 144 patients. The median (interquartile range) age was 67.7 years (55.8-75.8 years). The final diagnosis was an infectious disease in 19 patients (13.2%), cancer in 23 (16%), inflammatory disease in 48 (33%), and miscellaneous diseases in 12 (8.3%). No diagnosis was made in 29.2% of the cases; half of the remaining had a spontaneously favorable outcome. Fever was observed in 63 patients (43%). Positron emission tomography coupled with CT was determined to be very useful in 19 patients (13.2%), useful in 37 (25.7%), not useful in 63 (43.7%), and misleading in 25 (17.4%). The median diagnostic delay (ie, the time interval between the first admission and a confirmed diagnosis) was significantly shorter in the useful (71 days [38-170 days]) and very useful (55 days [13-79 days]) groups than that in the not useful group (175 days [51-390 days]; P<.001). The median time interval between the PET/CT scan and the diagnosis was twice as long in the not useful group than that in the pooled misleading, useful, or very useful groups (P=.03). In a univariate analysis, the poor overall condition (P=.007) and the absence of fever (P=.005) were predictive of usefulness of PET/CT. CONCLUSION: Positron emission tomography coupled with CT seems to be useful in the diagnosis of IUO and might shorten the diagnostic delay.