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Li J, Grimes K, Saade J, Tomlinson JJ, Mestre TA, Schade S, Weber S, Dakna M, Wicke T, Lang E, Trenkwalder C, Salmaso N, Frank A, Ramsay T, Manuel D, Mollenhauer B, Schlossmacher MG. Development of a simplified smell test to identify Parkinson's disease using multiple cohorts, machine learning and item response theory. NPJ Parkinsons Dis 2025; 11:85. [PMID: 40268961 PMCID: PMC12019603 DOI: 10.1038/s41531-025-00904-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2024] [Accepted: 03/12/2025] [Indexed: 04/25/2025] Open
Abstract
To develop a simplified smell test for identifying patients with Parkinson's disease (PD), we reevaluated the Sniffin'-Sticks-Identification-Test (SST-ID) and University-of-Pennsylvania-Smell-Identification-Test (UPSIT), using three case-control studies. These included 301 patients with PD or dementia with Lewy bodies (DLB), 68 subjects with multiple-system atrophy (MSA) or progressive supranuclear palsy (PSP), and 281 healthy controls (HC). Scents were ranked by area-under-the-curve values for group classification and results leveraged by 8 published studies with 5853 individuals. PD/DLB patients showed markedly worse olfaction than controls, whereas scores for MSA/PSP subjects were intermediate. We identified and validated a subset of 7 shared odorants that performed similarly to the traditional 16-scent SST-ID and 40-scent UPSIT tests in distinguishing PD/DLB from HC. There, the identification of 4 or fewer scents out of 7 served as an effective cut-off between the two groups. We also identified a critical role for distractors (from correct answers) and age on olfaction performance.
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Affiliation(s)
- Juan Li
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
- Methodological and Implementation Research Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA.
| | - Kelsey Grimes
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Methodological and Implementation Research Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Joseph Saade
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Julianna J Tomlinson
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Tiago A Mestre
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Methodological and Implementation Research Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada
- Department of Medicine, University of Ottawa, Ottawa, ON, Canada
- Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, ON, Canada
| | | | - Sandrina Weber
- Department of Neurology, University Medical Center Goettingen, Goettingen, Germany
| | - Mohammed Dakna
- Department of Neurology, University Medical Center Goettingen, Goettingen, Germany
| | | | | | - Claudia Trenkwalder
- Paracelsus-Elena-Klinik, Kassel, Germany
- Department of Neurology, University Medical Center Goettingen, Goettingen, Germany
| | - Natalina Salmaso
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | - Andrew Frank
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada
- Memory Program, Bruyère Research Institute, Ottawa, ON, Canada
| | - Tim Ramsay
- Methodological and Implementation Research Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- The Methods Centre, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
| | - Douglas Manuel
- Methodological and Implementation Research Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Medicine, University of Ottawa, Ottawa, ON, Canada
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
| | - Brit Mollenhauer
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA.
- Paracelsus-Elena-Klinik, Kassel, Germany.
- Department of Neurology, University Medical Center Goettingen, Goettingen, Germany.
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Goettingen, Germany.
| | - Michael G Schlossmacher
- Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA.
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada.
- Department of Medicine, University of Ottawa, Ottawa, ON, Canada.
- Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, ON, Canada.
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Mitchell E, Mattjie C, Bestwick JP, Barros RC, Schuh AF, Simonet C, Noyce AJ. Hyposmia in Parkinson's disease; exploring selective odour loss. NPJ Parkinsons Dis 2025; 11:67. [PMID: 40185787 PMCID: PMC11971265 DOI: 10.1038/s41531-025-00922-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2024] [Accepted: 03/20/2025] [Indexed: 04/07/2025] Open
Abstract
Smell loss is a frequent and early manifestation of Parkinson's disease (PD), serving as a sensitive - albeit nonspecific - clinical biomarker1. The notion that PD causes odour-selective hyposmia has been debated for three decades. Previous studies have used healthy controls as the comparator; this is problematic given the majority presumably display normal olfactory function. Using University of Pennsylvania Smell Identification Test data from the Parkinson's Progression Markers Initiative, we trained eight machine learning models to distinguish 'PD hyposmia' (n = 155) from 'non-PD hyposmia' (n = 155). The best-performing models were evaluated on an independent validation cohort. While specific responses (e.g. mistaking pizza for bubble gum) were impactful across models, at best only 63% of PD cases were correctly identified. Given we used a balanced data set, 50% accuracy would be achieved by random guessing. This suggests that PD-related hyposmia does not exhibit a unique pattern of odour selectivity distinct from general hyposmia.
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Affiliation(s)
- Eleanor Mitchell
- Centre for Preventive Neurology, Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK
| | - Christian Mattjie
- Centre for Preventive Neurology, Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK
- Machine Learning Theory and Applications Lab, School of Technology, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Jonathan P Bestwick
- Centre for Preventive Neurology, Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK
| | - Rodrigo C Barros
- Machine Learning Theory and Applications Lab, School of Technology, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Artur F Schuh
- Department of Pharmacology, Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil
- Neurology Department, Hospital de Clínicas de Porto Alegre, Rio Grande do Sul, Brazil
| | - Cristina Simonet
- Centre for Preventive Neurology, Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK
| | - Alastair J Noyce
- Centre for Preventive Neurology, Wolfson Institute of Population Health, Faculty of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK.
- Department of Clinical & Movement Neurosciences, UCL Institute of Neurology, London, UK.
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