Patent ID: 8323903

Claim:
A method for determining the presence of a desired target in a biological sample, said method comprising: a) combining in a reaction vessel, at least one target-binding antibody comprising an Fc region with a labeling protein to form a labeling mixture, wherein the target-binding antibody is capable of binding to the target, and in the presence of the target, binds to it, wherein the target-binding antibody is non-covalently bound to the labeling protein, wherein the labeling protein comprises a monovalent anti-Fc antibody fragment comprising an Fc binding region that non-covalently binds to the Fc region on the target-binding antibody, wherein the labeling protein is independently covalently linked to one or more labels at a region other than the Fc binding region, wherein the one or more labels may be the same or different; b) combining in the reaction vessel, the labeling mixture with a capture component to form a immunolabeling complex, wherein the capture component is capable of binding to labeling protein that did not bind to the target-binding antibody, and when unbound labeling protein is present, binds to the unbound labeling protein; c) removing the immunolabeling complex from the reaction vessel; d) combining the immunolabeling complex with the sample; and e) detecting the presence or absence of the label whereby the presence or absence of said target is determined.