Patent ID: 7202041

Claim:
An immunoreaction measurement method for measuring an antigen or antibody contained as a subject substance in a sample, comprising the steps of: (A) mixing said sample; at least one compound selected from the group consisting of tartaric acid, itaconic acid, straight-chain dicarboxylic acids expressed by the chemical formula (1): HOOC(CH 2 ) n COOH (n is an integer from 1 to 7), and the salts of these dicarboxylic acids; and an antibody or antigen as a specifically binding substance capable of specifically binding to said subject substance, to obtain an acidic reaction solution; and (B) detecting in said reaction solution an antigen-antibody complex generated by an antigen-antibody reaction of said subject substance and said specifically binding substance, wherein the pH of said reaction solution is set to 5.0 to 6.0 when said compound comprises at least one selected from the group consisting of said straight-chain dicarboxylic acids and salts of these dicarboxylic acids, and the pH of said reaction solution is set to 4.5 to 5.0 when said compound comprises at least one selected from the group consisting of said tartaric acid, said itaconic acid and salts of these dicarboxylic acids.