ELISA is short for enzyme linked immunosorbent assay. This is a diagnostic medical test to see if there is any present antibody or antigen in the body of a person. Its purpose is for calibrating the immunity of a person in terms of diseases and viruses. It identifies the protein concentration in the bodily fluids of a person.

HIV tests are one of the many examples of ELISA. It detects antibodies which are connected to the virus that are inside the blood of the patient. As for thyroid glands, Thyroid ELISA kits are used in most laboratories for further studying the present protein molecules. With this, other various kits are existent depending on what use they are.

In science and in certain industries, this test is used as one of the many tools of plant pathology and also with quality control check. Other examples this test is used for in diagnostic clinics are for food allergy and illegal drugs. The reading for this is determined by the vibrancy and intensity of the color changes in swabs whenever a sample is tested.

There are two most common types of ELISA tests. The indirect detects protein or the antibody and the example for this is as what was mentioned, HIV tests. The other one is the capture or sandwich. It detects the antigen by capturing them between two antibodies. The hormone human chorionic gonadotropin, or hCG, is detected using sandwich. One example of this would be pregnancy tests.

There are many ways to collect samples from the patient or donor. Two common ways are from blood or urine, which by now, you have already guessed, is taken during tests in clinics and hospitals. For blood samples, they are placed inside a test tube and sent to the laboratories for further analysis. Inside the laboratory, the actual testing would begin.

As for human blood, it is made up of plasma, red cells, and white blood cells. What is needed for the tests are blood serum. It is plasma that is stripped off with the clotting behaviour through centrifuge which spins the samples in high speed to separate the blood in different parts. The cells would be on the bottom while the serum stays on top.

There are enzyme substrate combinations that can be used for detection. The one enzyme used the most is Horseradish Peroxidase. This cleaves or separates the substrate molecules Ortho Phenylenediamine Dihydrochloride, or OPD, and Tetramethylbenzidine, or TMB, from each other. The result would be a yellow color when these two are separated. Then a plate reader is used to measure the optical density.

When the patient is thought to have a known disease or condition, the blood or urine sample will have specific antibodies which will react to the testings. These antibodies will latch itself to the antigens which are the specific bonding agents in the test. After that, the samples will be washed with a solution in order for it to remove everything else except for the antigens or also the antibodies.

To get results through color changes, enzyme solutions would be added to the samples to get either a positive or a negative result. But there is a certain possibility for the test results to give a false positive. A false positive is when a sample has no infection or whatever but still gives a positive result. Even so, ELISA tests are reliable and considered to be a standard in the immunology community.