ELISA is a diagnostic test that detects the presence of antibodies or antigens from diseases like HIV in a patient’s blood. It involves obtaining a blood sample, adding it to an ELISA plate, washing, and measuring the degree of color change. False results can be avoided by including positive and negative controls.
The ELISA procedure begins in the clinic, with a blood draw from the patient. A few steps are then followed using the ELISA test kit in the laboratory. The test will detect the presence of antibodies or antigens from a disease, such as HIV, in the blood. The stages include adding various substances and washing and the results are usually measured by a change in colour.
The enzyme immunoassay (ELISA), also known as an enzyme immunoassay (EIA), is used as a diagnostic test. It is best known as a diagnostic test for HIV. The test plate usually consists of 96 small wells in which a specific antigen is immobilized. If antibody is present in the serum sample, it will bind to the antigen, enabling detection by the various steps of the ELISA procedure.
The first step in the ELISA procedure is to obtain a sample from the patient. This is done by a nurse, under sterile conditions. Blood is usually taken from a vein in the arm or hand. A tourniquet is placed on the arm to inflate the vein and facilitate the procedure, and the skin is cleaned where the needle will be inserted. You may feel a small prick as the needle goes in and the blood will be collected in a sterile tube.
After the blood sample has been taken, it is transferred to the laboratory where the rest of the ELISA procedure will be performed by a laboratory technician. The blood sample is first added to the wells of the ELISA plate. If the specific antibody is present, it binds to the antigen. The plate is then washed, using a swab, to remove unbound antibodies.
A second antibody is then added, usually of animal origin, to which an enzyme is bound, which will bind to the antigen-antibody complex. The plate is washed again, to remove the excess. The enzyme is color reactive when a substrate is added at the end of the ELISA procedure. It is the measure of the degree of color change that gives the result.
The ELISA procedure must be followed carefully to avoid false results. A positive and negative control is included with most ELISA plates to minimize such false results. When testing for HIV, a positive result is usually followed up with a second confirmatory test, often of a different type, such as a Western Blot.
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