Plasma phosphorylated tau217 discordance with amyloid status in an ethnically diverse mixed memory clinic cohort

We characterized patients with discordant plasma p-tau217 results and amyloid status determined by the Aβ42/p-tau181 CSF ratio or Aβ-PET biomarkers in an ethnically diverse mixed memory clinic cohort. Among 539 patients, 83.9% had concordant biomarker profiles, while 13.4% were amyloid negative and plasma p-tau217 positive discordant, and 2.8% were amyloid positive and plasma p-tau217 negative discordant. Discordant groups differed in cognitive syndrome severity and etiological diagnosis, but no other variables reached significance. However, analyses indicated small effects of BMI, kidney function, and certain neurological conditions. Amyloid negativity and plasma p-tau217 positivity discordance may reflect plasma p-tau217 detecting early amyloid pathology not detected by CSF or Aβ-PET. Further research is needed to clarify mechanisms underlying discordant biomarker profiles.