The National Institute of Virology (NIV), Pune has developed an immunoassay, an Enzyme-Linked Immunosorbent Assay – ELISA, to detect the antibodies that the body develops in response to infection with the new coronavirus SARS-CoV-2. The test will detect the IgG antibodies present in the blood samples. ELISA is commonly used to detect HIV infection. The Comptroller General of Drugs has granted commercial production and marketing authorization to Zydus Cadila, the first time that India has developed an indigenous ELISA test for coronavirus. The company licensed to manufacture ELISA will have about a month to make the tests available, as collection of 30,000 random blood samples from the general population in the 75 critical districts will begin in the third week. of May.
What is an ELISA test ?
An enzyme-linked immunosorbent test, also called an ELISA or EIA, is a test that detects and measures antibodies in the blood. This test can be used to determine if you have antibodies related to certain infectious conditions. Antibodies are proteins that your body makes in response to harmful substances called antigens. An ELISA test may be used to diagnose:
- HIV, which causes AIDS
- Lyme disease
- pernicious anemia
- Rocky Mountain spotted fever
- squamous cell carcinoma
- varicella-zoster virus, which causes chickenpox and shingles
- Zika virus
ELISA is often used as a screening tool before ordering further testing. A doctor may suggest this test if you have signs or symptoms of the above conditions. Your doctor can also order this test if you want to exclude any of these conditions.
The ELISA test involves taking a sample of your blood. First, a health professional will clean your arm with an antiseptic. Then, a tourniquet or band will be applied around your arm to create pressure and make your veins swell with blood. Next, a needle will be placed into one of your veins to take a small blood sample. When enough blood has been drawn, the needle will be removed and a small bandage will be placed on the arm where the needle was. You will be asked to maintain pressure at the site where the needle was inserted for a few minutes to reduce blood flow. This procedure should be relatively painless, but your arm may throb a little after it’s done. The blood sample will be sent to a laboratory for analysis. In the laboratory, a technician will add the sample to a Petri dish containing the specific antigen related to the condition for which the test is being performed. If your blood contains antibodies to the antigen, the two will unite. The technician will verify this by adding an enzyme to the Petri dish and observing how your blood and antigen react. It can have the condition if the content of the plate changes color. The degree of change caused by the enzyme allows the technician to determine the presence and amount of antibodies.
There are very few risks associated with this test. These include: infection, feeling faint, bruising, bleeding more than usual.
What do the results mean?
The way test results are reported varies depending on the laboratory performing the analysis. It also depends on the condition for which the test is performed. Your doctor should discuss your results and what they mean. Sometimes a positive result means you don’t have the condition. False positives and false negatives can occur. A false positive result indicates that you have a condition that you do not actually have. A false negative result indicates that you do not have a condition when you really do. For this reason, you may be asked to repeat ELISA again in a few weeks, or your doctor may order more sensitive tests to confirm or refute the results.