When we contract an infection, our body’s immune system produces a protein called antibodies to fight against the harmful antigens present in the virus. Thus, for a medical expert to detect the condition, they recommend an ELISA test to the affected individual. According to the National Library Of Medicine, Enzyme-Linked Immunosorbent Assay is the standard technology to detect antibodies, antigens, proteins and hormones in the blood.
“The ELISA technology is used to detect various parameters of the infectious disease, starting from all types of hepatitis, toxoplasmosis, herpes simplex virus, HIV, dengue and many more,” says Dr Saranya Narayan, Chief Technical Director & Microbiologist, Neuberg Diagnostics, Chennai.
It takes about two to three hours to complete the testing process. According to Dr Sharanya the demand for ELISA tests increases during the months of September, October, and November months. “We see a peak in these months because there is a significant rise in infectious diseases like dengue,” said Dr Saranya.
Dr Ambanna Gowda, senior consultant physician and Diabetologist, Sparsh Hospital, Infantry Road, Bengaluru, however, explains that sometimes the infection might not be detected immediately. “If the doctor’s doubt persists on whether or not the person has an infection, then the sample can be sent for another round of testing after a week,” he says.
ELISA test explained
A person need not fast before taking the ELISA test. Taking hepatitis B infection as an example, Dr Saranya explains the role of the ELISA test in detail below:
A blood sample from a person suspected of the infection is added to a microtiter plate. The plate is already coated with antibodies against hepatitis B. If the blood sample contains hepatitis B antigens, it will react to the antibodies present on the plate. An enzyme will be added to the antigen-antibody to bind the mixture. Next, a substrate (reagent) will be added which works as a medium in which a chemical reaction occurs. If the mixture turns copper-sulphate-coloured, the infection has been detected. If there is no colour formed, the person may not be suffering from Hepatitis B.
Why do you need an ELISA test?
“We conduct an ELISA test to detect any form of infection. For instance, if we detect dengue infection, we usually check for the specific IgM (Immunoglobulin M) or neutralising antibodies. This test is also recommended to be taken to identify the infection of the diseases at its on-set or early stages,” says Dr Gowda.
Dr Gowda also mentions that the test is done during the first week of the illness. “The symptoms for dengue can show within the 4th or 5th day of the infection. There are chances that the person may turn positive for an infection for around 12 weeks (due to the presence of dead viral remnants). Hence it is essential to conduct tests when a person has symptoms,” said Dr Gowda.
When talking about the advantages and disadvantages of ELISA testing, Dr Gowda explains, “One notable advantage of conducting the ELISA testing is that doctors can confirm the recent infection a person has contracted at an early stage in a limited time frame. Once the test comes out positive, we can carry further tests to rectify the diseases,” he says.
However, this test is not useful to find a specific variant of the infection detected and can only be found in another series of tests that the doctor will recommend.
Takeaways
- An ELISA test is done to measure or detect a person’s antibodies or antigen of a condition.
- The various recent infections that can be detected through this test includes hepatitis, toxoplasmosis, herpes simplex virus, HIV and dengue.
- Though ELISA tests detect an infection at an early stage, they cannot find the specific variant.
