Method for diagnosing alzheimer's disease using signal peptide as indicator

A method for aiding detection of Alzheimer's disease, the method comprising:

• analyzing to determine a presence or absence of an Alzheimer's-associated signal peptide or analyzing to determine a degree of abundance of the Alzheimer's-associated signal peptide when the Alzheimer's-associated signal peptide is present in a bodily fluid from a test subject, and
• comparing the presence or absence of the Alzheimer's-associated signal peptide or the degree of abundance of the Alzheimer's-associated signal peptide in the bodily fluid from the test subject with a reference level set based on results obtained by analyzing the presence or absence of the Alzheimer's-associated signal peptide or the degree of abundance of the Alzheimer's-associated signal peptide in a bodily fluid from at least one healthy subject, wherein
• a molecular weight of the Alzheimer's-associated signal peptide is:
• 1629.17±2, 1767.38±2, 1900.43±2, 1933.29±2, 1966.96±2 1996.12±2, 2187.30±2, 2196.08±2, 2196.64±2, or 2240.20±2, wherein
• an amino acid sequence constituting the Alzheimer's-associated signal peptide is any of the amino acid sequences represented by SEQ ID NOS:
• 1 to 75;
• and wherein analyzing to determine the presence or absence of the Alzheimer's-associated signal peptide or to determine the degree of abundance of the Alzheimer's-associated signal peptide in the bodily fluid from the test subject comprises testing with a mass spectrometer and
• immobilizing the bodily fluid on a thermoplastic resin before the presence or absence of the Alzheimer's-associated signal peptide or the degree of abundance of the Alzheimer's-associated signal peptide in the bodily fluid is tested, wherein the presence or absence of the Alzheimer's-associated signal peptide or the degree of abundance of the Alzheimer's-associated signal peptide in the bodily fluid immobilized on the thermoplastic resin is determined by testing with a matrix assisted laser desorption/ionization-time-of-flight mass spectrometry.