Detection of amyloid β protein in the urine of Alzheimer's disease patients and healthy individuals

To seek for a new valid biomarker using non-invasive specimens for the diagnosis of Alzheimer's disease (AD) and mild cognitive impairment (MCI), we carried out the detection of amyloid β (Aβ) protein in urine. Ten-millilitre urine samples were first sedimented with trichloroacetic acid, and the pellets were resuspended for further analysis by Western blotting with anti-Aβ antibody. The detection sensitivity of the method was 40 pg/ml. Rates of subjects positive for monomeric Aβ according to their clinical dementia rating (CDR) were 11.1% for CDR 0, 62.5% for CDR 0.5, 83.3% for CDR 1, 54.5% for CDR 2 and 0% for CDR 3. A single Aβ band relative to the CDR score reflects an alteration in the production, solubility and clearance of Aβ in the brain. Thus, the method could be used as both a diagnostic and monitoring tool in assessing AD and MCI patients during disease-modifying therapies.