What is the term for a biochemical test that detects the presence of a macromolecule or small molecule in solution using antibodies or antigens?

The term for a biochemical test that detects the presence of a macromolecule or small molecule in solution using antibodies or antigens is immunoassay. Immunoassays leverage the specific binding properties of antibodies to their corresponding antigens to identify and quantify substances—this characteristic is what makes them incredibly useful in various biological and medical applications, such as disease diagnosis and monitoring therapeutic drug levels.

Immunoassays can yield results for a range of molecules including proteins, hormones, and other biomolecules, offering both sensitivity and specificity. They employ techniques that might involve labeled antibodies to facilitate detection, allowing for the measurement of an analyte's concentration in a test sample.

In contrast, bioreactors are systems for growing organisms or cells for research or production, but they are not specifically designed for detection through antibodies. Chromatography involves separating components in a mixture based on their physical or chemical properties, and while it is useful for analyzing mixtures, it does not use antibodies for detection. Electrophoresis separates charged molecules based on size and charge but does not inherently involve antibodies or the antigen-antibody interaction characteristic of immunoassays.