This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for mouse/rat Aβ (38-42) has been pre-coated onto a microtiter plate. Standards or samples are pipetted into the wells. After washing away any unbound substances, the HRP-labeled mouse/rat Aβ (1-16) antibody is added to each well and incubate. Following a washing to remove unbound substances, a substrate solution (TMB) is added to the wells and color develops in proportion to the amount of Aβ 1-42 bound in the initial step. The color development is stopped by the addition of acid and the intensity of the color is measured at a wavelength of 450nm. The concentration of Aβ 1-42 in the sample is then determined by comparing the O.D of samples to the standard curve. The concentration of antigen is directly proportional to the optical density measured in the wells. Sample Types: serum and plasma. Range: 1.56 - 100 pg/ml. Sensitivity: 0.05 pg/ml. Time: 3 hours ? Alzheimer's Disease (AD) is the most common neurodegenerative disorder in elderly people. It has been demonstrated that AD has biological causes and is characterized by the presence of senile plaques and neurofibrillary tangles mainly in cerebral cortex and hippocampus brain regions. Beta-Amyloid (1-40) (Aβ40) and beta-Amyloid (1-42) (Aβ42) are the main components of the above plaques; however, other forms of beta-Amyloid peptides are also present. Both peptides are cleaved from the Amyloid Precursor Protein (APP) by β-secretase and γ-secretase enzymes. Many studies suggest that Aβ42 or/and Aβ43 are required to initiate formation of amyloid plaques and neurofibrills that leads to the neurodegeneration, while Aβ40 is less neurotoxic.