Abstract: Two different antibodies that specifically bind to tau protein or phosphorylated tau protein are used. One of the two different antibodies is a first antibody immobilized on a support or labeled with a molecule capable of binding to the support, and the other of the two different antibodies is a second antibody labeled without being immobilized on the support. The tau protein includes an N-terminal domain, a C-terminal domain, and an intermediate domain located between the N-terminal and C-terminal domains. Epitopes recognized by the first and second antibodies are each an amino acid sequence contained in the intermediate domain or an amino acid sequence contained in the N-terminal domain. One of the first and second antibodies is first subjected to an antigen-antibody reaction with the blood sample, and the other of the first and second antibodies is subsequently subjected to an antigen-antibody reaction with the blood sample.

Abstract: The present disclosure provides a method for detecting Alzheimer's cognitive impairment or mild cognitive impairment, comprising: measuring an amount of homocysteic acid in a biological sample from a subject who suffers or possibly suffers from a neurological disease, and detecting Alzheimer's cognitive impairment or mild cognitive impairment based on the measured amount of the homocysteic acid.

Abstract: Provided is a method for aiding diagnosis of a neurodegenerative disease in a subject with a light physical burden. The method for aiding diagnosis of the neurodegenerative disease, comprising: a first assessment step of assessing a risk of the neurodegenerative disease based on an amount of homocysteine acid in a biological sample obtained from the subject; a second assessment step of assessing a risk of the neurodegenerative disease based on an amount of an inflammatory factor, a pituitary gland secretion, or an autonomic nerve secretion in the biological sample obtained from the subject or based on a measured value obtained from a brain image of the subject; and a step of determining whether the subject has the neurodegenerative disease based on the results of the first assessment and the second assessment.