Patent ID: 8900882

Claim:
A method of assaying the level of complex AB of substance A and substance B in a sample which is likely to contain complex AB, comprising: i) determining level P, which is the level of substance A present in complex AB and in a free form in the sample, through the steps of mixing the sample, a substance A-specific binding partner C, and fine particles carrying both substance A or an analogue thereof and substance B or an analogue thereof, in order to allow competition for a specific binding reaction with the specific binding partner C between substance A present in complex AB and in a free form in the sample and substance A or the analogue carried on the fine particles; measuring the degree of agglutination of said fine particles via the specific binding partner C; and determining level P based on the degree of agglutination of said fine particles via the specific binding partner C; ii) determining level Q, which is the level of substance B present in complex AB and in a free form in the sample, through the steps of: mixing the sample, a substance B-specific binding partner D, and the fine particles carrying both substance A or the analogue and substance B or the analogue, in order to allow competition for a specific binding reaction with the specific binding partner D between substance B present in complex AB and in a free form in the sample and substance B or the analogue carried on the fine particles; measuring the degree of agglutination of said fine particles via the specific binding partner D; and determining level Q based on the degree of agglutination of said fine particles via the specific binding partner D; iii) determining level R through the steps of; mixing the sample, the substance A-specific binding partner C, the substance B-specific binding partner D, and the fine particles carrying both substance A or the analogue and substance B or the analogue, in order to allow competition for a specific binding reaction with the specific binding partner C between substance A present in complex AB and in a free form in the sample and substance A or the analogue carried on the fine particles as well as competition for a specific binding reaction with the specific binding partner D between substance B present in complex AB and in a free form in the sample and substance B or the analogue carried on the fine particles; measuring the degree of agglutination of said fine particles via the specific binding partners C and D; and determining level R based on the degree of agglutination of said fine particles via the specific binding partners C and D; and iv) calculating level a of complex AB according to the formula α=P+Q−R; wherein said substance A-specific binding partner C is an anti-A antibody; and wherein said substance B-Specific binding partner D is an anti-B antibody.