Serial CSF α-Synuclein Seed Amplification Results Show High Consistency in PPMI

A longitudinal observational analysis published in Movement Disorders evaluated the intraindividual consistency of cerebrospinal fluid α-synuclein seed amplification assay results using the Amprion assay. The PPMI cohort included 1,238 participants with more than one result: 633 with Parkinson’s disease, 563 classified as prodromal, and 42 healthy controls. Samples spanned a median of 2.0 years, with a range of 0.4–11.4 years.

Among participants with Parkinson’s disease, 96% of initially positive participants remained positive (474/493; 95% CI, 94%–98%), while 92% of initially negative participants remained negative (116/126; 95% CI, 86%–96%). In the prodromal group, corresponding proportions were 99% (303/307) and 95% (234/247). Among healthy controls, 89% of initially positive participants remained positive (16/18), and 87% of initially negative participants remained negative (20/23).

These findings support longitudinal consistency of assay status, including negative results in Parkinson’s disease and positive results in healthy controls. However, consistency alone does not establish diagnostic accuracy or usefulness for monitoring disease progression. The healthy-control sample was small, and only the abstract was available; it does not explain why the reported positive and negative subgroup denominators do not include every participant in each clinical group.