Plasma p-tau217 correlates strongly with cerebrospinal fluid Aβ42 and increases over a ten-year period in amyloid-positive, non-demented very old men.

BackgroundPlasma phosphorylated tau217 (p-tau217) is a robust biomarker of Alzheimer's disease (AD) pathology. However, its full potential as a dynamic marker has still not been verified in very old persons, i.e., those with the highest incidence of AD.ObjectiveTo examine the cross-sectional and longitudinal associations between plasma p-tau217 concentration and cerebrospinal fluid (CSF) AD biomarkers. Further, to investigate the performance of p-tau217 as a predictor of amyloid status in a cohort of very old men.MethodsCSF AD biomarkers were analyzed in thirty-five 89-year-old men. Amyloid-β (Aβ) positivity was defined according to CSF Aβ42 level. Plasma p-tau217 concentration was measured at the mean age of 82, 87, and 91. Incident dementia diagnoses in survivors were identified through medical records up to the age of 102.ResultsPlasma p-tau217 strongly correlated with CSF Aβ42 concentration in Aβ-positive (n = 16, Spearman ρ: rho = -0.63, p = 0.009) but not in Aβ-negative (n = 19, rho = 0.111, p = 0.652) men and predicted Aβ status (area under the curve, AUC 0.91). Plasma p-tau217 increased over ten years in the Aβ-positive group, while it remained unchanged in the negative group (p = 0.018).ConclusionsOur findings indicate that plasma p-tau217 is a predictor of brain Aβ deposition also in very old individuals.