Types of ELISA Tests
Antibody testing is usually done on a blood sample, often using an enzyme-linked assay called an ELISA or EIA. In this test, a person's serum is allowed to react with virus proteins that have been produced in the laboratory. If the person has been infected with HIV, the antibodies in the serum will bind to the HIV proteins, and the extent of this binding can be measured. Negative EIA results are usually available in a day or so.
What is ELISA?
ELISA is an abbreviation for "enzyme-linked immunosorbent assay."
What is an ELISA test?
An ELISA test uses components of the immune system (such as IgG or IgM antibodies) and chemicals for the detection of immune responses in the body (for example, to infectious microbes). The ELISA test involves an enzyme (a protein that catalyzes a biochemical reaction). It also involves an antibody or antigen (immunologic molecules). Examples of the uses of an ELISA test includes to diagnose infections such as HIV (human immunodeficiency virus) and some allergic diseases like food allergies. ELISA tests are also known as an immunosorbent assay.
What is the use of an ELISA test?
ELISA tests are primarily used for the detection of proteins (as opposed to small molecules and ions such as glucose and potassium). The substances detected by ELISA tests can include hormones, viral antigens (dengue fever, for example), bacterial antigens (TB, for example), and antibodies that the body has made in response to infection (antibodies to hepatitis B, for example) or vaccination.
What is an ELISA kit?
An ELISA kit is a commercially available ELISA test that usually contains pre-coated polystyrene plates, detection antibodies, and usually all of the chemicals needed to perform an ELISA test. However, special kits can be purchased with substances designated by the customer.
How do health care workers perform an ELISA test?
Health care personnel who perform the test are trained laboratory technicians who use special kits that measure the antigens' interactions with the antibodies in the kit. They will inform your doctor of the test results.
Picture of micro-pipetting samples into a polystyrene plate for an ELISA test kit; Photo by James Gathany/CDC
How does ELISA testing work?
There are variations of the ELISA test (see below), but the most utilized type consists of an antibody attached to a solid surface (polystyrene plate). This antibody has affinity for (will latch on to) the substance of interest, such as a hormone, bacteria, or another antibody. For example, human chorionic gonadotropin hormone (HCG), the commonly measured protein which indicates pregnancy, can be detected by ELISA. A mixture of purified HCG linked to an enzyme and the test sample (blood or urine) are added to the test system. If no HCG is present in the test sample, then only the linked enzyme will bind to the solid surface. The more substance of interest that is present in the test sample, the less linked enzyme will bind to the solid surface. The more of the substance of interest is present it will cause a reaction and show up on the test plate in some way, such as a change in color of the solution (or like a pregnancy test "two pink lines" or a "+" mark).
Medically Reviewed by a Doctor on 2/23/2017