title: Sniffing the diagnosis: Olfactory testing in neurodegenerative parkinsonism.
abstract: To determine the diagnostic utility of olfactory testing in patients with neurodegenerative parkinsonism.
  
  
  
  The Sniffin' Sticks test battery for assessment of odor identification, discrimination, and threshold was applied to patients with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) as well as healthy controls (HC). Two different cohorts were analyzed: A PD/healthy control that included PD patients and HC as well as a PD/diseased control cohort for which patients PD, MSA and PSP were recruited. The former cohort was exploited to calculate cut-off values that discriminate PD patients from HC with a sensitivity (sensitivity-weighted cut-off) or specificity (specificity-weighted cut-off) exceeding 95%, respectively. The PD/diseased controls cohort was used to determine the diagnostic accuracy using these cut-off values in discriminating patients with neurodegenerative parkinsonism.
  
  
  
  PD patients (n = 67) performed significantly worse in olfactory testing than HC (n = 41) and patients with MSA (n = 23) or PSP (n = 23). There was no significant difference in olfactory function between MSA and PSP patients. Diagnostic performance of the identification subscore was similar to the sum score of the Sniffin' Sticks test (AUC identification test 0.94, AUC sum score 0.96), while threshold and discrimination subscores were inferior. In patients with parkinsonism, the specificity-weighted cut-off predicted a diagnosis of PD with a sensitivity and specificity of 76.6 and 87.0%, respectively. The discriminative value of this cut-off in separating PD from MSA was 76.7% (sensitivity) and 95.7% (specificity). The corresponding, prevalence-adjusted positive predictive value of olfactory testing exceeded 95%.
  
  
  
  Our data suggest that assessment of olfactory function, particularly odor identification, can be useful to discriminate PD from atypical parkinsonian disorders, particularly MSA patients.
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Krismer
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Pinter
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Mueller
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Mahlknecht
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Nocker
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Reiter
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Djamshidian-Tehrani
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: S M
authors.initials: SM
authors.lastname: Boesch
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: G K
authors.initials: GK
authors.lastname: Wenning
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Scherfler
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: W
authors.initials: W
authors.lastname: Poewe
authors.affiliation: Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria. Electronic address: klaus.seppi@tirol-kliniken.at.
authors.forename: K
authors.initials: K
authors.lastname: Seppi
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000175:diagnosis / Q000503:physiopathology; D009812:Odorants; D020734:Parkinsonian Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D012903:Smell / Q000502:physiology*
keywords: Multiple system atrophy; Olfaction; Parkinson's disease; Progressive supranuclear palsy; Sniffin' sticks