page_title: Immunoassay
section_title: Classifications and formats
hierarchical_section_title: Immunoassay / Classifications and formats
caption_attribution_description: English: This image illustrates the components and principle behind a competitive homogeneous immunoassay.
context_page_description: An immunoassay is a biochemical test that measures the presence or concentration of a macromolecule or a small molecule in a solution through the use of an antibody or an antigen. The molecule detected by the immunoassay is often referred to as an "analyte" and is in many cases a protein, although it may be other kinds of molecules, of different size and types, as long as the proper antibodies that have the adequate properties for the assay are developed. Analytes in biological liquids such as serum or urine are frequently measured using immunoassays for medical and research purposes.
  Immunoassays come in many different formats and variations. Immunoassays may be run in multiple steps with reagents being added and washed away or separated at different points in the assay. Multi-step assays are often called separation immunoassays or heterogeneous immunoassays. Some immunoassays can be carried out simply by mixing the reagents and sample and making a physical measurement. Such assays are called homogeneous immunoassays, or less frequently non-separation immunoassays.
  The use of a calibrator is often employed in immunoassays.
context_section_description: Immunoassays can be run in a number of different formats. Generally, an immunoassay will fall into one of several categories depending on how it is run.
caption: In a competitive, homogeneous immunoassay unlabeled analyte displaces bound labelled analyte, which is then detected or measured.
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