Plasma tau in Alzheimer disease

Neurology. 2016 Oct 25;87(17):1827-1835. doi: 10.1212/WNL.0000000000003246. Epub 2016 Sep 30.

Abstract

Objective: To test whether plasma tau is altered in Alzheimer disease (AD) and whether it is related to changes in cognition, CSF biomarkers of AD pathology (including β-amyloid [Aβ] and tau), brain atrophy, and brain metabolism.

Methods: This was a study of plasma tau in prospectively followed patients with AD (n = 179), patients with mild cognitive impairment (n = 195), and cognitive healthy controls (n = 189) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and cross-sectionally studied patients with AD (n = 61), mild cognitive impairment (n = 212), and subjective cognitive decline (n = 174) and controls (n = 274) from the Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably (BioFINDER) study at Lund University, Sweden. A total of 1284 participants were studied. Associations were tested between plasma tau and diagnosis, CSF biomarkers, MRI measures, 18fluorodeoxyglucose-PET, and cognition.

Results: Higher plasma tau was associated with AD dementia, higher CSF tau, and lower CSF Aβ42, but the correlations were weak and differed between ADNI and BioFINDER. Longitudinal analysis in ADNI showed significant associations between plasma tau and worse cognition, more atrophy, and more hypometabolism during follow-up.

Conclusions: Plasma tau partly reflects AD pathology, but the overlap between normal aging and AD is large, especially in patients without dementia. Despite group-level differences, these results do not support plasma tau as an AD biomarker in individual people. Future studies may test longitudinal plasma tau measurements in AD.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Alzheimer Disease / blood*
  • Alzheimer Disease / cerebrospinal fluid
  • Alzheimer Disease / complications
  • Amyloid beta-Peptides / cerebrospinal fluid
  • Brain / diagnostic imaging
  • Brain / metabolism
  • Brain / pathology
  • Cognition Disorders / etiology
  • Cohort Studies
  • Female
  • Fluorodeoxyglucose F18 / pharmacokinetics
  • Humans
  • Male
  • Neuropsychological Tests
  • Positron-Emission Tomography
  • Psychiatric Status Rating Scales
  • tau Proteins / blood*

Substances

  • Amyloid beta-Peptides
  • tau Proteins
  • Fluorodeoxyglucose F18