Appropriateness of applying CSF biomarker cutoffs from Alzheimer’s disease to Parkinson’s disease

Background While cutoffs for abnormal levels of the cerebrospinal fluid (CSF) biomarkers amyloid β 1-42 (Aβ 1-42), total tau (t-tau), phosphorylated (p-tau), and ratios t-tau/Aβ p-tau/Aβ 1-42, have been established in Alzheimer’s disease (AD), biologically relevant not studied extensively Parkinson’s (PD). We aim to assess suitability diagnostic accuracy AD-derived CSF biomarker PD population. Method Baseline longitudinal data on biomarkers, cognitive diagnoses, PET imaging 423 newly diagnosed patients with from Progression Markers Initiative (PPMI) cohort were used evaluate AD compared optimal derived PPMI cohort. Result Using as gold standard pathology, cutoff Aβ was higher than cutoff, lower cutoffs, their confidence intervals (CIs) did overlap cutoffs. Optimal t-tau p-tau predict impairment significantly CIs Conclusion amyloid-PET positivity differ populations. The presence additional pathologies such alpha-synuclein may lead disease-specific characteristics.