{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T21:59:04Z","timestamp":1791410344443,"version":"4.3.3"},"posted":{"date-parts":[[2026,4,3]]},"group-title":"Neurology","reference-count":9,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,4,3]],"date-time":"2026-04-03T00:00:00Z","timestamp":1775174400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,4,3]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>Studies reporting alpha-synuclein seed amplification assay (aSyn-SAA) results are often cross-sectional. Here we investigated the intra-individual consistency of aSyn-SAA results over time from participants in the Parkinson\u2019s Progression Marker Initiative (PPMI). A total of 1238 participants had &gt;1 CSF aSyn-SAA result for analysis (Parkinson\u2019s disease [PD]=633, prodromal =563, healthy control [HC]=42) which were collected over a median (min, max) of 2.0 (0.4, 11.4) years. Emphasis was placed on evaluating consistency in less common results such as aSyn-SAA- PD participants, aSyn-SAA+ HC and conversion rates from aSyn-SAA negative to positive results prodromal participants. Of aSyn-SAA+ PD participants, 96% (474\/493, 95%CI 94-98%) remained positive in subsequent samples, and 92% (116\/126, 95%CI 86-96%) of aSyn-SAA- PD participants remained negative. 99% (303\/307, 95%CI 97-99%) of aSyn-SAA+ prodromal participants remained positive, and 95% (234\/247, 95%CI 91-97%) of aSyn-SAA- prodromal participants remained negative. 89% (16\/18, 95%CI 67-97%) of aSyn-SAA+ HC participants remained positive, and 87% (20\/23, 95%CI 68-95%) of aSyn-SAA- HC participants remained negative. These results confirm a high consistency of aSyn-SAA results over time, even in less expected results.<\/jats:p>","DOI":"10.64898\/2026.04.01.26349969","type":"posted-content","created":{"date-parts":[[2026,4,3]],"date-time":"2026-04-03T23:10:11Z","timestamp":1775257811000},"source":"Crossref","is-referenced-by-count":2,"title":["Consistency of Serial CSF alpha-Synuclein Seed Amplification Assay Results in the Parkinson\u2019s Progression Marker Initiative"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4111-0102","authenticated-orcid":false,"given":"David G.","family":"Coughlin","sequence":"first","affiliation":[{"name":"Department of Neurosciences, University of California San Diego, La Jolla CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Caroline","family":"Gochanour","sequence":"additional","affiliation":[{"name":"Department of Biostatistics, University of Iowa, Iowa City IA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jie","family":"Yin","sequence":"additional","affiliation":[{"name":"Department of Biostatistics, University of Iowa, Iowa City IA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luis","family":"Concha-Marambio","sequence":"additional","affiliation":[{"name":"Research and Development Department, Amprion, San Diego, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carly","family":"Farris","sequence":"additional","affiliation":[{"name":"Research and Development Department, Amprion, San Diego, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yihua","family":"Ma","sequence":"additional","affiliation":[{"name":"Research and Development Department, Amprion, San Diego, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David-Erick","family":"Lafontant","sequence":"additional","affiliation":[{"name":"Department of Biostatistics, University of Iowa, Iowa City IA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Edwin","family":"Jabbari","sequence":"additional","affiliation":[{"name":"Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2347-1644","authenticated-orcid":false,"given":"Tanya","family":"Simuni","sequence":"additional","affiliation":[{"name":"Department of Neurology, Northwestern University, Chicago IL"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ken","family":"Marek","sequence":"additional","affiliation":[{"name":"Institute for Neurodegenerative Disease, New Haven CT"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas F.","family":"Tropea","sequence":"additional","affiliation":[{"name":"Institute for Neurodegenerative Disease, New Haven CT"},{"name":"Department of Neurology, University of Pennsylvania, Philadelphia PA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"name":"the Parkinson\u2019s Progression Marker Initiative","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026040615100607000_2026.04.01.26349969v1.1","doi-asserted-by":"publisher","DOI":"10.1016\/S1474-4422(23)00109-6"},{"issue":"10","key":"2026040615100607000_2026.04.01.26349969v1.2","doi-asserted-by":"crossref","first-page":"812","DOI":"10.1002\/acn3.338","article-title":"Alpha-synuclein RT-Qu IC in the CSF of patients with alpha-synucleinopathies","volume":"3","year":"2016","journal-title":"Ann Clin Transl 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