Reference intervals for plasma amyloid-β, total tau, and phosphorylated tau181 in healthy elderly Chinese individuals without cognitive impairment

Abstract

Background: Plasma amyloid-β (Aβ) peptides and tau proteins are promising biomarkers of Alzheimer’s disease (AD), not only for predicting Aβ and tau pathology but also for differentiating AD from other neurodegenerative diseases. However, reference intervals for plasma biomarkers of AD in healthy elderly Chinese individuals have not yet been established. Methods: Biomarkers of AD were measured using single-molecule array (Simoa) assays in plasma samples from 193 healthy, cognitively unimpaired Chinese individuals aged 50–89 years. The 95% reference intervals for plasma Aβ42, Aβ40, t-tau, p-tau181, and derived ratios were calculated by using log-transformed parametric methods. Results: Plasma Aβ42, Aβ40, and p-tau181 levels were positively correlated with age, while the Aβ42/Aβ40 ratio was negatively correlated with age. The 95% reference intervals for plasma Aβ42 and Aβ40 were 2.72–11.09 pg/mL and 61.4–303.9 pg/mL, respectively, and the 95% reference intervals for plasma t-tau and p-tau181 were 0.20–3.12 pg/mL and 0.49–3.29 pg/mL, respectively. The 95% reference intervals for the Aβ42/Aβ40 ratio, p-tau181/t-tau ratio, and p-tau181/Aβ42 ratio were 0.022–0.064, 0.38–6.34, and 0.05–0.55, respectively. Conclusion: Reference intervals for plasma biomarkers of AD may assist clinicians in making accurate clinical decisions.