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You might have heard of ELISA test kits before, but not really understand what they are for. And the name ELISA is not really a woman’s name, but the term actually has a more scientific origin. ELISA stands for “enzyme-linked immunosorbent assay”, which is a method commonly used in laboratories to diagnose various diseases in the form of ELISA tests. Using blood or urine samples, the ELISA test measures a particular protein or substance such as hormones, infectious agents, drugs, antibodies, and antigens to detect diseases or the body’s immune responses.

What the ELISA test is for

ELISAs are used to test and help diagnose the presence of different illnesses and conditions. A few of the frequent uses of ELISA test kits are to detect HIV, Hepatitis B or C, and also pregnancy. Besides checking for diseases, ELISAs are also used to measure the levels of your antibodies to check if you have already been vaccinated against diseases like rubella and mumps.

ELISA tests can also detect if you have dust and food allergies and avoid future health risks. When checking for illicit drug usage, laboratories use ELISAs to look for traces of cocaine and methamphetamines in the body. Antibodies are also measured by ELISAs to diagnose lupus and rheumatoid arthritis in patients.

How the ELISA test is performed

The healthcare provider draws blood from a vein from the inside of the elbow or the back of the hand. After collecting the blood sample into a glass tube or onto a slide or test strip, the puncture area is covered with bandage to stop further bleeding. Instead of a needle, a sharp tool called a lancet is used to puncture an infant’s or toddler’s skin to make it bleed.

The laboratory checks the blood sample for the targeted substance and is linked to the enzyme in the ELISA test. If it substance is present, the test solution changes its color. The results are mostly either positive or negative, which means your body either has the antibody or it doesn’t. In case of semi-quantitative or results with values, ELISA tests are used to measure the levels or the amount of the substance, such as when measuring for hormone levels in pregnancy tests.

How the ELISA test works

ELISA tests come in different variations but the most basic one is when testing for the presence of antibodies or antigens. In the case of an HIV test, a portion of the HIV virus is used as the antigen and is attached to a tube or plate. The patient’s serum is mixed into the tube, and if the antibodies to the antigen are present, then they will bind to it. A second antibody that can recognize the HIV antibodies is added into the mix and binds to any bound antibody. This other antibody also links with an enzyme to hasten a chemical reaction. Finally, a substance that reacts with the enzyme on the antibody is added in order to make a colored product. Thus, if the color changes, then the result is positive. If there are no antibodies for that particular antigen, there will be no reaction and no change of color occurs.

False positive or false negative results may occur, which is a huge drawback of ELISA tests. Therefore, it is recommended to follow up with a confirmatory test or a different type of test to verify. Getting a negative result does not always mean that an infection has not occurred. Some antibodies are not produced right after the infection and this may nullify the result of the test. For example, HIV antibodies appear in blood only after six weeks after exposure to the virus.

Categories: Some Kind of Medicine

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