ELISA is a testing process that detects substances to identify diseases, allergies, and illegal drugs in the body. It uses a chemical reaction between a patient’s sample and a specific laboratory sample to detect antibodies, hormones, and proteins. ELISA was invented in 1971 as a safer alternative to radioimmunoassay. There are two common types of ELISA tests: direct and indirect. The patient’s serum is poured into wells coated with an antigen, and after incubation, another set of antibodies is added to detect human antibodies. An enzyme substrate is added to produce a visible color reaction indicating a positive result.
An ELISA test is a testing process that detects substances in order to identify certain diseases, allergies and illegal drugs in the body. It is also known to be used to detect human immunodeficiency virus (HIV). Some of the substances it can detect are antibodies, hormones, and proteins. The main principle behind the ELISA test is that a chemical reaction between a patient’s liquid sample and a specific laboratory sample indicates the presence of a certain substance associated with a specific disease or medical condition. ELISA, as an acronym, stands for “enzyme-linked immunosorbent assay”.
The invention and development of the ELISA assay occurred because there was a need for a safer test method other than the radioimmunoassay, which uses radioactivity to produce a chemical reaction. In the 1960s, two separate groups of scientists led by Stratis Avrameas and GB Pierce succeeded in associating certain antibodies with certain enzymes and producing a chemical reaction from the combination. With this knowledge at hand, two Stockholm University scientists, Peter Perlmann and Eva Engvall, invented the ELISA method, publishing their experiments and the system behind the test in 1971. Since then, the ELISA test has been used worldwide, although radioimmunoassay is still available due to its lower cost.
There are two common types of ELISA tests: the direct method and the indirect method, the latter being more commonly used. The first step would be to extract a sample from the patient, usually blood or urine, both of which may undergo a separation process to extract the clear serum containing the antibodies. An ELISA kit often contains a plate that contains 96 mini-containers called “wells,” which will be coated with an antigen that may have a reaction to an antibody present. An antigen is often thought of as a foreign substance that the body attacks by producing specific antibodies, so if a patient has acquired an antigen from a certain disease, his serum should contain antibodies that match said antigen.
The patient serum will then be poured into the wells and then incubated to adhere the antibodies to the protein coat. After the incubation period, the wells are rinsed to remove remaining serum and other antibodies that have not bound to the coating. Another set of antibodies extracted from animals, usually rats, will be poured into the wells to detect human antibodies, and another incubation period will take place and the animal antibodies will be washed off again. An enzyme substrate will then be added so that the reaction can be visibly seen in color. Typically, a strong shade of color will indicate a positive result, meaning the patient has the disease or other tested medical condition.
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