Non-Phosphorylated Tau as a Potential Biomarker of Alzheimer's Disease: Analytical and Diagnostic Characterization

J Alzheimers Dis. 2017;55(1):159-170. doi: 10.3233/JAD-160448.


Background: Virtually nothing is known about a potential diagnostic role of non-phospho-epitopes of Tau (Non-P-Tau) in cerebrospinal fluid (CSF).

Objective: To establish and analytically and clinically characterize the first assay capable to measure concentrations of Non-P-Tau in human CSF.

Methods: An antibody (1G2) was developed that selectively binds to the Tau molecule non-phosphorylated at the positions T175 and T181, and was used in establishing a sandwich ELISA capable to measure Non-P-Tau in human CSF, following analytical and clinical validation of the method.

Results: The 1G2 antibody shows decreasing reactivity to tau peptides containing phosphorylation mainly at positions T175 and T181. Detection limit of the assay is 25 pg/ml; the coefficients of variation (CVs) of the optical densities of the repeated standard curves were between 3.6-15.9%. Median intra-assay imprecision of double measurements was 4.8%; inter-assay imprecision was in the range of 11.2% - 15.3%. Non-P-Tau concentrations are stable in the CSF samples sent to distinct laboratories under ambient temperature; inter-laboratory variation was approximately 30%. The Non-P-Tau CSF concentrations were highly significantly increased in patients with Alzheimer's disease in stage of mild cognitive impairment or dementia (AD/MCI, n = 58, 109.2±32.0 pg/mL) compared to the non-demented Controls (n = 42, 62.1±9.3 pg/mL, p < 0.001). At the cut-off of 78.3 pg/mL, the sensitivity and the specificity were 94.8% and 97.6%, respectively.

Conclusion: For the first time, an assay is reported to reliably measure concentrations of non-phosphorylated Tau in human CSF.

Keywords: Biomarkers; cerebrospinal fluid; phosphorylation; tau.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Alzheimer Disease / cerebrospinal fluid*
  • Animals
  • Biomarkers / cerebrospinal fluid
  • Cells, Cultured
  • Cognitive Dysfunction / cerebrospinal fluid
  • Enzyme-Linked Immunosorbent Assay / methods
  • Epitope Mapping
  • Female
  • Humans
  • Immunoglobulin G
  • Male
  • Mice, Inbred BALB C
  • Phosphorylation
  • Protein Stability
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Specimen Handling / methods
  • Temperature
  • tau Proteins / cerebrospinal fluid*
  • tau Proteins / genetics


  • Biomarkers
  • Immunoglobulin G
  • MAPT protein, human
  • tau Proteins