Methods and systems for species-on-species immunoassay detection

A method for determining the presence of a target compound in a sample, the method comprising:

• providing (a) a target-binding antibody comprising a region that binds non-covalently to a target compound, (b) a quenching composition comprising quenching compounds, wherein the quenching compounds comprise enriched serum components, and wherein the enriched serum components are at a concentration greater than 4-fold that normally found in serum and (c) a labeling composition comprising one or more labeling proteins, wherein each of the labeling proteins comprises a monovalent Fab antibody fragment comprising a region that binds non-covalently to the target-binding antibody, and wherein each of the labeling proteins is linked covalently to one or more labels, and wherein each of the labeling proteins is monovalent and capable of binding non-covalently to at least one of the quenching compounds;
• introducing the target-binding antibody into the labeling composition to form an active product composition comprising (a) a labeled antibody complex, which comprises the target-binding antibody and one or more labeling proteins bound non-covalently to the target-binding antibody, and (b) free labeling proteins, which are not bound non-covalently to any target-binding antibodies;
• introducing the quenching composition to the active product composition to form a quenched active product composition comprising the labeled antibody complex and quenched labeling proteins, wherein each of the quenched labeling proteins comprises one or more quenching compounds bound non-covalently to one or more labeling proteins;
• and
• introducing at least a portion of the quenched active product composition to a sample;
• and
• following the introduction of at least a portion of the quenched active product composition to the sample, analyzing the sample to determine the presence or absence of the target compound in the sample.