title: Utility of FDG PET/CT for Differential Diagnosis of Patients Clinically Suspected of IgG4-Related Disease.
abstract: OBJECTIVE
  We investigated the capacity of F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) to differentially diagnose immunoglobulin G4-related disease (IgG4-RD) in clinically suspected patients.
  
  
  METHODS
  Subjects were 94 clinically suspected patients who had tissue IgG4 staining (n = 85) or serum IgG4 greater than 135 mg/dL (n = 9) and underwent FDG PET/CT within 40 days. Clinical, serologic, pathological, and PET/CT findings were analyzed. Binary logistic regression analysis was performed to assess the diagnostic performance of PET/CT.
  
  
  RESULTS
  Final diagnosis was IgG4-RD in 28, malignancy in 29, IgG4-unrelated inflammation in 35, and undetermined cause in 2 subjects. Patients with IgG4-RD had lower maximum standardized uptake value (SUVmax) of FDG uptake in lesions (4.6 ± 1.7 vs 7.1 ± 5.0) and higher submandibular gland SUVmax (2.8 ± 1.0 vs 2.3 ± 0.6) and were more likely to have diffuse/heterogeneous uptake pattern (78.6% vs 54.8%). The relation between SUVmax of lesions and histopathological findings was weak. On binary logistic regression analysis, lesion SUVmax, submandibular gland SUVmax, and multiorgan involvement were significant predictors of IgG4-RD and provided an area under the receiver operating characteristics curve of 0.824. With optimum criteria, FDG PET/CT had a sensitivity of 85.7% and specificity of 66.1% for diagnosing IgG4-RD.
  
  
  CONCLUSIONS
  FDG PET/CT findings may have the capacity to potentially differentiate IgG4 RD from other diseases in clinically suspected patients.
authors.affiliation: From the Departments of *Nuclear Medicine, †Pathology, and ‡Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Joohee
authors.initials: J
authors.lastname: Lee
authors.forename: Seung Hyup
authors.initials: SH
authors.lastname: Hyun
authors.forename: Seokhwi
authors.initials: S
authors.lastname: Kim
authors.forename: Duk-Kyung
authors.initials: DK
authors.lastname: Kim
authors.forename: Jong Kyun
authors.initials: JK
authors.lastname: Lee
authors.forename: Seung Hwan
authors.initials: SH
authors.lastname: Moon
authors.forename: Young Seok
authors.initials: YS
authors.lastname: Cho
authors.forename: Yearn Seong
authors.initials: YS
authors.lastname: Choe
authors.forename: Byung-Tae
authors.initials: BT
authors.lastname: Kim
authors.forename: Kyung-Han
authors.initials: KH
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000000981:diagnostic imaging* / Q000276:immunology; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D007074:Immunoglobulin G; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18