Ultrasensitive Detection of Plasma Amyloid-beta as a Biomarker for Cognitively Normal Elderly Individuals at Risk of Alzheimer's Disease

• Background: Aberrant amyloid-beta (A beta) deposition in the brain occurs two decades prior to the manifestation of Alzheimer's disease (AD) clinical symptoms and therefore brain A beta load measured using PET serves as a gold standard biomarker for the early diagnosis of AD. However, the uneconomical nature of PET makes blood markers, that reflect brain A beta deposition, attractive candidates for investigation as surrogate markers. Objective: Investigation of plasma A beta as a surrogate marker for brain A beta deposition in cognitively normal elderly individuals. Methods: Plasma A beta(40) and A beta(42) concentrations were measured using the ultrasensitive Single Molecule Array (Simoa) assay in 95 cognitively normal elderly individuals, who have all undergone PET to assess brain A beta deposition. Based on the standard uptake value ratios (SUVR) obtained from PET imaging, using the tracer F-18-Florbetaben, plasma A beta was compared between 32 participants assessed to have low brain A beta load (A beta-, SUVR <1.35) and 63 assessed to have high brain A beta load (A beta+, SUVR >= 1.35). Results: Plasma A beta(42)/A beta(40) ratios were lower in the A beta+ group compared to the A beta- group. Plasma A beta(40) and A beta(42) levels were not significantly different between A beta- and A beta+ groups, although a trend of higher plasma A beta(40) was observed in the A beta+ group. Additionally, plasma A beta(42)/A beta(40) ratios along with the known AD risk factors, age and APOE epsilon 4 status, resulted in A beta+ participants being distinguished from A beta- participants based on an area under the receiver operating characteristic curve shown to be 78%. Conclusion: Plasma A beta ratios in this study are a potential biomarker for brain A beta deposition and therefore, for preclinical AD. However, this method to measure plasma A beta needs further development to increase the accuracy of this promising AD blood biomarker.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Neurologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Neurology (hsv//eng)

Keyword

Alzheimer's disease

blood biomarkers

plasma amyloid-beta

plasma amyloid-beta ratios

preclinical

dementia

quantification

association

deposition

decline

Neurosciences & Neurology

Publication and Content Type

ref (subject category)

art (subject category)