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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.<\/jats:p>","DOI":"10.1038\/s41531-025-00904-5","type":"journal-article","created":{"date-parts":[[2025,4,23]],"date-time":"2025-04-23T08:26:38Z","timestamp":1745396798000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Development of a simplified smell test to identify Parkinson\u2019s disease using multiple cohorts, machine learning and item response theory"],"prefix":"10.1038","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1565-2477","authenticated-orcid":false,"given":"Juan","family":"Li","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0545-3813","authenticated-orcid":false,"given":"Kelsey","family":"Grimes","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-5913-3575","authenticated-orcid":false,"given":"Joseph","family":"Saade","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2997-5162","authenticated-orcid":false,"given":"Julianna J.","family":"Tomlinson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6973-7479","authenticated-orcid":false,"given":"Tiago A.","family":"Mestre","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6316-6804","authenticated-orcid":false,"given":"Sebastian","family":"Schade","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5713-2141","authenticated-orcid":false,"given":"Sandrina","family":"Weber","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8341-0360","authenticated-orcid":false,"given":"Mohammed","family":"Dakna","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9779-4692","authenticated-orcid":false,"given":"Tamara","family":"Wicke","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5748-1376","authenticated-orcid":false,"given":"Elisabeth","family":"Lang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6407-1199","authenticated-orcid":false,"given":"Claudia","family":"Trenkwalder","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9661-5194","authenticated-orcid":false,"given":"Natalina","family":"Salmaso","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew","family":"Frank","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8478-8170","authenticated-orcid":false,"given":"Tim","family":"Ramsay","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0912-0845","authenticated-orcid":false,"given":"Douglas","family":"Manuel","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"name":"aSCENT-PD Investigators","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8437-3645","authenticated-orcid":false,"given":"Brit","family":"Mollenhauer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0394-0300","authenticated-orcid":false,"given":"Michael G.","family":"Schlossmacher","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2025,4,23]]},"reference":[{"key":"904_CR1","first-page":"450939","volume":"2011","author":"A Haehner","year":"2011","unstructured":"Haehner, A, Hummel, T & Reichmann, H Olfactory loss in Parkinson\u2019s disease. 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(2016)."}],"container-title":["npj Parkinson's Disease"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.nature.com\/articles\/s41531-025-00904-5.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/www.nature.com\/articles\/s41531-025-00904-5","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/www.nature.com\/articles\/s41531-025-00904-5.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,4,23]],"date-time":"2025-04-23T08:26:43Z","timestamp":1745396803000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.nature.com\/articles\/s41531-025-00904-5"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,4,23]]},"references-count":47,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2025,12]]}},"alternative-id":["904"],"URL":"https:\/\/doi.org\/10.1038\/s41531-025-00904-5","relation":{"has-preprint":[{"id-type":"doi","id":"10.1101\/2024.08.09.24311696","asserted-by":"object"}]},"ISSN":["2373-8057"],"issn-type":[{"value":"2373-8057","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,4,23]]},"assertion":[{"value":"8 October 2024","order":1,"name":"received","label":"Received","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"12 March 2025","order":2,"name":"accepted","label":"Accepted","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"23 April 2025","order":3,"name":"first_online","label":"First Online","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"Peer reviewed grants that funded the work are listed in Acknowledgements. M.G.S. reports royalties from Eli Lilly (administered via MassGeneral Brigham Integrated Healthcare System and unrelated to the topic of this study), and payment for travel and hotel as an invited speaker at the AD\/PD 2024 conference. In 2024, M.G.S co-founded NeuroScent, Inc. to develop a simplified testing platform for hyposmia. B.M. reports honoraria for consultancy and\/or educational presentations from GE, Bial, Roche, Biogen, and AbbVie. B.M. is a member of the executive steering committee of the Parkinson Progression Marker Initiative of the Michael J. Fox Foundation for Parkinson\u2019s Research. M.G.S. and B.M. received research funding from Aligning Science Across Parkinson\u2019s (ASAP, CRN). C.T. reports personal payment from the UCB Data Safety Monitoring Board in Early PD and the Advisory Board of Boehringer, Ono, Bial, Roche in Early PD (both not related to the current manuscript), and several leadership roles in the Movement Disorder Society, including the past-president (no payment). None of the other authors declares any competing financial interests.","order":1,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}}],"article-number":"85"}}