Patent ID: 8802446

Claim:
A method for measuring cystatin C in a human body fluid, comprising: (1) contacting a human body fluid with (a) first insoluble carrier particles coated with a first anti-human cystatin C monoclonal antibody which has affinity for cystatin C and (b) second insoluble carrier particles coated with a second anti-human cystatin C monoclonal antibody which has affinity for cystatin C, wherein the first anti-human cystatin C monoclonal antibody has an affinity for cystatin C that is higher than the second anti-human cystatin C monoclonal antibody, the first anti-human cystatin C monoclonal antibody has a dissociation constant of less than 1 nM, the second anti-human cystatin C monoclonal antibody on the second insoluble carrier particles recognizes an epitope of cystatin C that is different from the epitope recognized by the first anti-human cystatin C monoclonal antibody on the first insoluble carrier particles, wherein the dissociation constant of the second anti-human cystatin C monoclonal antibody divided by the dissociation constant of the first anti-human cystatin C monoclonal antibody is two or greater, the first insoluble carrier particles are coated with from 1% to less than 4% by weight of the first anti-human cystatin C monoclonal antibody, and the second insoluble carrier particles are coated with from 1% to less than 4% weight of the second anti-human cystatin C monoclonal antibody, (2) measuring the amount of cystatin C bound to the first insoluble carrier particles and the second insoluble carrier particles, and (3) correlating the amount of cystatin C bound to the first insoluble carrier particles and the second insoluble carrier particles with the amount of cystatin C in the human body fluid.