title: Combined DaT imaging and olfactory testing for differentiating parkinsonian disorders.
abstract: OBJECTIVE
  Dopamine transporter (DaT) imaging with single photon emission computed tomography (SPECT) detects loss of striatal dopaminergic innervation with very high sensitivity. It cannot readily distinguish idiopathic Parkinson's disease (iPD) and dementia with Lewy bodies (DLB) from atypical disorders (aPD). However, most iPD/DLB patients are hyposmic, whereas the majority of aPD patients were reported to have intact olfaction. For this reason, we conducted a longitudinal follow-up study to investigate the power of combined DaT imaging and olfactory testing to predict the final diagnosis of the patients.
  
  
  METHODS
  A total of 129 patients received [123I]FP-CIT SPECT and olfactory testing at baseline assessment. Clinical follow-up 30 ± 12 months later was the diagnostic standard of truth. A normative dataset of 24 healthy controls was used for comparison.
  
  
  RESULTS
  Baseline DaT imaging predicted a dopamine-deficient diagnosis with 98% sensitivity and 98% specificity. The combined DaT/olfactory testing correctly classified 91% of patients as iPD/DLB (PPV 91%). The PPV rose to 97% or greater in anosmic patients. In contrast, only 45% of aPD patients were categorised correctly by combined DaT/olfactory testing - mainly because of the presence of normosmic iPD patients.
  
  
  CONCLUSIONS
  In patients with an abnormal DaT SPECT, hyposmia yields an a posteriori likelihood of iPD/DLB of > 90%. In contrast, a finding of normosmia only increases the a posteriori likelihood of aPD to approximately the 50%.
authors.affiliation: Department of Nuclear Medicine and PET Centre, Aarhus University Hospital, Aarhus C, Denmark.
authors.forename: P
authors.initials: P
authors.lastname: Borghammer
authors.forename: K
authors.initials: K
authors.lastname: Knudsen
authors.forename: K
authors.initials: K
authors.lastname: Østergaard
authors.forename: E H
authors.initials: EH
authors.lastname: Danielsen
authors.forename: N
authors.initials: N
authors.lastname: Pavese
authors.forename: A
authors.initials: A
authors.lastname: Arveschoug
authors.forename: H
authors.initials: H
authors.lastname: Bluhme
authors.forename: M
authors.initials: M
authors.lastname: Bode
authors.forename: A
authors.initials: A
authors.lastname: Morsing
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D050483:Dopamine Plasma Membrane Transport Proteins / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020961:Lewy Body Disease / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000000981:diagnostic imaging*; D020734:Parkinsonian Disorders / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000706:statistics & numerical data*; D014463:Ultrasonography
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins