Immunoassay kits are among our most useful and popular products. When used as directed, they can provide sensitive and specific quantitation of specific molecules in complex biological fluids. For large molecules with multiple epitopes, we provide Sandwich ELISA kits. Sandwich ELISA uses two antibodies, one to capture the target molecule and a second to detect it. The advantage of this method is its linear detection and large reading range. However, this method is only viable for large molecules.
For small molecules with only one epitope such as eicosanoids or hormones, a Competitive ELISA can be employed. Although these assays have a smaller useful dynamic range and the results are inversely related to the analyte concentration, they can provide very accurate results if used properly. This method involves a single antibody coated to the plate. The sample analyte competes for binding sites with an analyte conjugated to a detection enzyme. The amount of binding of the sample analyte is inverse to the amount of signal obtained.
For more information on ELISA and interpreting their results, please see the excellent review article by Sasaki and Mitchell below: