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Age but not diagnosis is the main predictor of plasma amyloid beta-protein levels

Hiroaki Fukumoto1, Marsha Tennis, Joseph J Locascio

  • 1Department of Neurology, Massachusetts General Hospital, Boston, MA 02129, USA.

Archives of Neurology
|July 23, 2003
PubMed
Abstract

Insights

Plasma amyloid beta (Abeta) levels increase with age but do not reliably diagnose Alzheimer's disease (AD) or mild cognitive impairment in sporadic cases. These biomarkers are not specific for early AD detection in routine clinical practice.

Area of Science:

  • Neuroscience
  • Biochemistry
  • Clinical Diagnostics

Background:

  • Plasma amyloid beta-protein (Abeta) levels, particularly Abeta42, are elevated in familial Alzheimer's disease (AD) and may indicate risk.
  • Previous research suggests high plasma Abeta42 levels can identify individuals at risk for developing AD.

Purpose of the Study:

  • To investigate characteristic changes in plasma Abeta40 and Abeta42 levels in sporadic AD.
  • To examine the relationship between plasma Abeta levels and clinical, demographic, and genetic factors in a prospective outpatient cohort.

Main Methods:

  • Analyzed plasma samples from 371 outpatients: sporadic AD (n=146), mild cognitive impairment (n=37), Parkinson disease (n=96), and non-demented controls (n=92).
  • Quantified plasma Abeta40 and Abeta42 using a sandwich enzyme-linked immunosorbent assay (ELISA) with specific capture and detector antibodies.

Main Results:

  • Plasma Abeta40 and Abeta42 levels significantly increased with age across all diagnostic groups.
  • After adjusting for age, no significant differences in plasma Abeta40 or Abeta42 levels were found among the four diagnostic groups.
  • Abeta levels did not correlate with memory impairment duration or cognitive scores in mild cognitive impairment and AD groups.
  • Plasma Abeta measures were not influenced by AD family history, APOE genotype, or common medications.

Conclusions:

  • Plasma Abeta levels demonstrate an age-dependent increase.
  • Contrary to findings in familial AD, plasma Abeta measures lack sensitivity and specificity for diagnosing mild cognitive impairment or sporadic AD.
  • Plasma Abeta levels are not reliable biomarkers for diagnosing sporadic Alzheimer's disease in a clinical setting.

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