The basic ELISA procedure, whose initials stand for enzyme-linked immunosorbent assay, test samples to determine if there is an antibody present and how much protein the antibodies bind within the sample’s volume. The test is inexpensive, accurate and free from using radioisotopes and expensive radiation counters that are required for radioimmunoassays.
Testing with the ELISA Method
Used to measure how much analyte is in a solution, ELISA tests were developed in the 1970s as an alternative to expensive and radioactive assays that use isotopes. This simpler alternative test requires less equipment and less time to perform, generates fewer risks for lab technicians and allows quantitative testing by analyzing specific and nonspecific interactions through serial binding to solid surfaces, such as polystyrene plates that change color in direct correlation to the amount of analyte in the given sample. ELISA tests can be used to detect:
• Immune system components
• Bacterial antigens
How the Test Works
Depending on what a sample is being tested for, you can test directly or indirectly or use a competition assay or sandwich ELISA. Direct ELISAs require fewer steps and reagents, are quick to perform and leave less room for errors. In a direct ELISA test, an antigen or protein is attached to a multiwell plate. If the sample contains an antibody to this specific antigen, it will be attracted to the material embedded in the multiwell plate. Coating the plate with an antibody that is geared to attract an antigen can also reverse the test. The test works both qualitatively and quantitatively by detecting specific substances and measuring how much of that substance is in a given sample.
The basic ELISA procedure has many clinical applications for medical diagnoses and food, biological and medical research. Anytime a foreign substance enters the blood or other bodily fluids, its antigens differ from the ambient antigens of the fluid. The immune system produces antibodies to destroy the foreign materials, and these antibodies attract the antigens that they are designed to destroy. ELISA tests can test for the antigens or the corresponding antibodies that the body produces to determine even minuscule amounts of specific microbiologicals. The test is ideal for testing blood, urine and other bodily fluids.