Beta Amyloid 42/40 Ratio Plasma (505725)

Use: The plasma A42/40 ratio is intended for use as an adjunct to diagnostic evaluations of Alzheimer's disease, including neurological and cognitive performance examinations and PET neuroimaging.

The diagnostic hallmarks of Alzheimer's disease (AD) are extracellular deposits of beta amyloid plaques and neurofibrillary tangles observed in the cortex and limbic brain region upon autopsy. The major molecular components of beta amyloid plaques and neurofibriiary tangles are beta amyloid 1-42 and tau protiens, respectively. The major beta amyloid metabolic products beta amyloid 1-42 and beta amyloid 1-40 are generated by beta and secretase enzymatic cleavage of the amyloid precursor protein (APP), with more hydrophobic beta amyloid 1-42 peptide aggregating to form amyloid plaques. Reduced concentrations of beta amyloid 42 in EDTA plasma are associated with increased retention of beta amyloid tracers in the brain beta amyloid plaques observed with positron emisson tomography (PET), and are inversely correlated. Low beta amyloid 42/40 ratios are more associated with patients having a clinical diagnosis of AD or beta amyloid PET positivity, whereas higher ratios are less associated with AD diagnosis or beta amyloid PET positivity.

Limitations: Samples that contain fibrin, red blood cells and other insoluble objects may lead to inaccurate results.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology: Sysmex chemiluminescence enzyme immunoassay (CLEIA)