title: Optimizing odor identification testing as quick and accurate diagnostic tool for Parkinson's disease.
abstract: The aim of this study was to evaluate odor identification testing as a quick, cheap, and reliable tool to identify PD.
  
  
  
  Odor identification with the 16-item Sniffin' Sticks test (SS-16) was assessed in a total of 646 PD patients and 606 controls from three European centers (A, B, and C), as well as 75 patients with atypical parkinsonism or essential tremor and in a prospective cohort of 24 patients with idiopathic rapid eye movement sleep behavior disorder (center A). Reduced odor sets most discriminative for PD were determined in a discovery cohort derived from a random split of PD patients and controls from center A using L1-regularized logistic regression. Diagnostic accuracy was assessed in the rest of the patients/controls as validation cohorts.
  
  
  
  Olfactory performance was lower in PD patients compared with controls and non-PD patients in all cohorts (each P < 0.001). Both the full SS-16 and a subscore of the top eight discriminating odors (SS-8) were associated with an excellent discrimination of PD from controls (areas under the curve ≥0.90; sensitivities ≥83.3%; specificities ≥82.0%) and from non-PD patients (areas under the curve ≥0.91; sensitivities ≥84.1%; specificities ≥84.0%) in all cohorts. This remained unchanged when patients with >3 years of disease duration were excluded from analysis. All 8 incident PD cases among patients with idiopathic rapid eye movement sleep behavior disorder were predicted with the SS-16 and the SS-8 (sensitivity, 100%; positive predictive value, 61.5%).
  
  
  
  Odor identification testing provides excellent diagnostic accuracy in the distinction of PD patients from controls and diagnostic mimics. A reduced set of eight odors could be used as a quick tool in the workup of patients presenting with parkinsonism and for PD risk indication. © 2016 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.|Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, United Kingdom.
authors.forename: Philipp
authors.initials: P
authors.lastname: Mahlknecht
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Raimund
authors.initials: R
authors.lastname: Pechlaner
authors.affiliation: Department of Neurology, Neuroscience Campus Amsterdam, VU University Medical Centre, Amsterdam, The Netherlands.|Divisions of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: Sanne
authors.initials: S
authors.lastname: Boesveldt
authors.affiliation: Study Center Confraternitaet-PKJ Vienna, Vienna, Austria.
authors.forename: Dieter
authors.initials: D
authors.lastname: Volc
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Bernardette
authors.initials: B
authors.lastname: Pinter
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Reiter
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Müller
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Krismer
authors.affiliation: Department of Neurology, Neuroscience Campus Amsterdam, VU University Medical Centre, Amsterdam, The Netherlands.
authors.forename: Henk W
authors.initials: HW
authors.lastname: Berendse
authors.affiliation: Department of Neurology, Leiden University Medical Centre, Leiden, The Netherlands.
authors.forename: Jacobus J
authors.initials: JJ
authors.lastname: van Hilten
authors.affiliation: Study Center Confraternitaet-PKJ Vienna, Vienna, Austria.
authors.forename: Albert
authors.initials: A
authors.lastname: Wuschitz
authors.affiliation: Department of Applied Systems Research and Statistics, Johannes Kepler University Linz, Linz, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schimetta
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Högl
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Atbin
authors.initials: A
authors.lastname: Djamshidian
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Nocker
authors.affiliation: Department of Medical Statistics, Informatics and Health Economics, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Göbel
authors.affiliation: Department of Neurology, Hospital of Bruneck, Bruneck, Italy.
authors.forename: Arno
authors.initials: A
authors.lastname: Gasperi
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kiechl
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Johann
authors.initials: J
authors.lastname: Willeit
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria. klaus.seppi@uki.at.
authors.forename: Klaus
authors.initials: K
authors.lastname: Seppi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D020329:Essential Tremor / Q000175:diagnosis*; D006801:Humans; D008875:Middle Aged; D055696:Olfactory Perception / Q000502:physiology*; D010300:Parkinson Disease / Q000150:complications / Q000175:diagnosis*; D020734:Parkinsonian Disorders / Q000175:diagnosis*; D010468:Perceptual Disorders / Q000175:diagnosis* / Q000209:etiology; D020187:REM Sleep Behavior Disorder / Q000175:diagnosis*; D012680:Sensitivity and Specificity
keywords: Parkinson's disease; diagnosis; olfactory dysfunction; parkinsonism; tremor