title: Diagnostic utility of (18)F-FDG PET/CT in inflammation of unknown origin.
abstract: OBJECTIVE
  The goal of this multicenter retrospective study was to evaluate the contribution of F-FDG PET/CT in the diagnosis of patients with inflammation of unknown origin (IUO). In addition, C-reactive protein (CRP) level and erythrocyte sedimentation rate were assessed as possible predictors for the outcome of F-FDG PET/CT.
  
  
  METHODS
  Inflammation of unknown origin was defined as prolonged and perplexing inflammation, with repeated CRP levels more than 20 mg/L or erythrocyte sedimentation rate more than 20 mm/h, body temperature of less than 38.3°C, and without a diagnosis after a variety of conventional diagnostic procedures.A total of 140 patients with IUO (67 men, 73 women; mean age, 64.2 years; age range, 18-87 years) underwent F-FDG PET/CT. F-FDG PET/CT was considered helpful when the imaging findings led to a diagnosis, either confirmed by histopathology, microbiological assays, clinical and imaging follow-up, or response to treatment.
  
  
  RESULTS
  In 104 patients (73%), a final diagnosis could be established as follows: infection in 35 patients, malignancy in 18 patients, noninfectious inflammatory disease in 44 patients, and a variety of uncommon conditions in 7 patients. F-FDG PET/CT was true positive in 95 patients, true negative in 30 patients (ie, self-limiting conditions), false positive in 6 patients, and false negative in 9 patients (predominantly systemic diseases). In this population, the positive predictive value, negative predictive value, and diagnostic accuracy of F-FDG PET/CT were 94%, 77%, and 89%, respectively. In a multivariate analysis, CRP was the only independent predictor for the outcome of F-FDG PET/CT.
  
  
  CONCLUSIONS
  F-FDG PET/CT correctly identified or excluded a causal explanation in approximately 90% of patients with IUO. However, a negative F-FDG PET/CT is indicative for a self-limiting condition only after systemic diseases are excluded by other diagnostic tests.
authors.affiliation: From the *Department of Nuclear Medicine, Medical Center Leeuwarden, Leeuwarden; †Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam; and ‡Department of Epidemiology, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Balink
authors.forename: Roel J
authors.initials: RJ
authors.lastname: Bennink
authors.forename: Nic J G M
authors.initials: NJ
authors.lastname: Veeger
authors.forename: Berthe L F
authors.initials: BL
authors.lastname: van Eck-Smit
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D007249:Inflammation / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18; D002097:C-Reactive Protein