Posted by : Moraliss Tuesday, October 7, 2014

By Jocelyn Davidson


ELISA is a medical test used in the enclosure of laboratories to figure out if a person has any certain disease or condition. It is an abbreviation from Enzyme Linked Immunosorbent Assay, where it tests the presence of certain protein molecules in a sample. Its main purpose is for testing the immunity of a patient.

One of these examples is for HIV, where it finds antibodies related to the virus inside the blood. Another would be for the thyroid glands, and the common equipment that are used in laboratories are Thyroid ELISA kits. These kits are used for studying the thyroid glands, as well as other types of kits are used for other body parts.

In general, ELISA is also used for tests in illegal drug use. It also helps determine the allergic reactions towards food for a person. It is widely used as a tool in plant pathology, and also in quality control check in some industries. How to determine this is through the intensity of the color change of each sample of the patient.

There are a few other ELISA tests that are available and existent, but the two common types are the indirect and capture. The indirect detects a certain protein or antibody, and an example for this is the HIV testing. The capture, also known as the sandwich, detects another protein which is the antigen, then captures it between two antibodies. An example is pregnancy tests where the detection of hCG or human chorionic gonadotropin is seen.

Various ways of collecting fluid samples from patients are possible, but the two most common are urine and blood. Urine and blood are placed in a container, or most likely a test tube, then are sent out to the hospital laboratories or clinics for analysis and testing. Inside the laboratory, the testing would start if there is any present antigen or antibody.

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.

Horseradish Peroxidase is an enzyme mostly used for detection where it separates Ortho Phenylenediamine Dihydrochloride and Tetramethylbenzidine. It results into a yellow color and for measuring the optical density, a plate reader would then be used. Light absorbance from OPD is 490 nanometers in wavelength, while TMB is at 450 nanometers.

In cases where the patient has revealed to have a disease or other conditions, the sample will have antibodies for that specific disease. The antibodies will then attach to these antigens that are the bonding agents in these ELISA tests. The samples would then be cleaned or washed away with a different solution so that the remaining in the sample would be the antigens or the antibodies that are clinging to the antigens.

Enzyme solutions would then be applied to the sample to determine if the color changes accordingly whether there it is a positive or negative result. Although there is a possibility for the test samples to return a false positive. This is when the sample of the patient does not have the infection but returns with a positive result. But regardless, ELISA tests are still considered the most reliable in the immunology community.




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