What is the principle behind ELISA tests?

The principle behind ELISA tests is the detection of specific antibodies or antigens in a sample using enzyme reactions.

ELISA, which stands for Enzyme-Linked Immunosorbent Assay, is a popular laboratory technique used to detect the presence of specific antibodies or antigens in a sample. This is achieved through a series of enzyme reactions, which produce a visible signal, usually a colour change, indicating the presence of the target substance.

The process begins with a 'capture' phase, where the sample is added to a plate coated with a specific antigen or antibody. If the target substance is present in the sample, it will bind to these molecules on the plate. The plate is then washed to remove any unbound substances.

Next, a 'detection' phase takes place. An enzyme-linked antibody or antigen, designed to bind to the target substance, is added to the plate. Again, the plate is washed to remove any unbound molecules.

The final 'readout' phase involves adding a substrate that the enzyme can act on. The enzyme catalyses a reaction with the substrate, producing a visible signal. This is usually a colour change, the intensity of which is proportional to the amount of target substance in the sample.

In summary, the principle behind ELISA tests is the use of specific antigen-antibody interactions and enzyme reactions to detect the presence and quantity of a particular substance in a sample. This makes ELISA a powerful tool in diagnostics and research, allowing for the detection of a wide range of substances, from hormones and drugs to bacteria and viruses.