Abstract: Disclosed is a method for measuring phosphorylated tau protein in a biological sample collected from a subject, comprising the steps of: preparing a measurement sample containing a non-capture bead and a capture bead to which an immune complex is bound, by forming the immune complex of the phosphorylated tau protein in the biological sample, a capture antibody and a detection antibody on the capture bead, in the presence of the non-capture bead; and detecting a signal derived from the immune complex in the measurement sample.

Abstract: Disclosed is a method for measuring phosphorylated tau protein in a biological sample collected from a subject, comprising the steps of: preparing a measurement sample containing a non-capture bead and a capture bead to which an immune complex is bound, by forming the immune complex of the phosphorylated tau protein in the biological sample, a capture antibody and a detection antibody on the capture bead, in the presence of the non-capture bead; and detecting a signal derived from the immune complex in the measurement sample.

Abstract: Provided is a measurement method of an A? oligomer by the ELISA method, particularly, a method of selectively measuring an A? oligomer with a comparatively high molecular weight. [Solving Means] A measurement method of an A? oligomer including the following steps: (a) a step of contacting a sample possibly containing an A? oligomer with a monoclonal antibody that recognizes a partial peptide consisting of the amino acid sequence shown by SEQ ID NO: 1, which is bound to an insoluble carrier (first antibody) to bind the A? oligomer with the first antibody; and (b) a step of reacting a labeled monoclonal antibody that recognizes a partial peptide consisting of the amino acid sequence shown by SEQ ID NO: 1 (second antibody) with the A? oligomer bound to the first antibody in step (a).