Role Of RT-PCR, ELISA IgG And COVID Antigen In COVID-19

Mr. Rajesh Patel, CEO – IVD India, Trivitron Healthcare

Since the spread of the coronavirus, the need of a reliable and accurate diagnostic testing has gained vital importance. Moreover, the symptoms of COVID-19 – cough, muscle pain, fever and difficulty in breathing can be a reflective of various other ailments like influenza, adding up to the essentiality of COVID-19 diagnostic tests for confirming COVID-19 cases. Additionally, these tests shall also serve the purpose of sero surveillance and act as an important tool to help study the virus and monitor the effectiveness of control measures.  Thanks to our technological advancements in diagnostics, we have made rapid progress in early diagnosis and contact tracing of the novel coronavirus. Three main tests have emerged as the gold standard in detection and treatment – the Reverse Transcription Polymerase Chain Reaction (RT-PCR), ELISA IgG & COVID Antigen.


Of the three, the extremely common and widely used scientific technique for over the past 20 to 30 years, the PCR, is now being used to detect the virus causing COVID-19 and is highly effective in detecting the genetic information of a virus, and has been aiding research and medicine by directly testing the presence of its RNA.

To detect the presence of the RNA, the test measures the viral RNA and converts it into DNA, makes copies of it using repeated temperature cycles in a PCR machine and uses fluorescent markers to detect the virus. If the amount of fluorescence goes above a certain level, the test confirms the presence of the virus.

RT-PCR tests are mostly preferred because they produce quick, sensitive and reliable results in close to 3-4 hours, except for when the samples have to be sent to external laboratories in which case the results may come in about 6-8 hours.

Since the technology is widely available, research and diagnostic laboratories have started manufacturing their own RT-PCR products, tests and machinery and even gone on to experiment with “all in one” kits thereby speeding up the process and negating the risks of contamination.


This test is designed to identify immunoglobulins (commonly called antibodies) against the novel corona virus. Antibodies are proteins produced by the immune system as a response against an invader i.e a pathogen. Found in serum or plasma (the liquid part of the blood) depending on the presence or absence of clotting factors.

The Coronavirus COVID-19 IgG ELISA Assay Kit is a serological plate-based assay technique that detects and quantifies substances such as peptides, proteins, antibodies and hormones.

This kit is currently the most used of the serological tests, and produces results in an average time of 2–5 hours. The test typically uses a surface coated with specific viral antigen to detect the corresponding patient antibodies (IgG, IgM, IgA) in samples.

ELISA assays are available in different formats including direct, competitive, and, the most commonly used, sandwich or double-antigen-bridging assay (DABA).

COVID Antigen

Unlike an RT-PCR test that studies the genetic disposition of the novel coronavirus from nasal samples, the Antigen test detects the presence of the nucleocapsid protein which is part of the SARS-CoV-2 virus that causes the coronavirus.

The COVID Antigen test reveals if a person is currently infected with a pathogen such as the SARS-CoV-2 virus. Once the infection wears off, the antigen disappears.

Antigen tests are an important complement to PCR testing, and are crucial to expand testing capacity. The beauty of antigen testing is that it is fast and gives quick results. It will allow healthcare workers to quickly isolate cases and treat them while tracing their contacts to cut the transmission chain.

Despite the efficacies of the above mentioned tests in the diagnosis and determination of the effects of the novel coronavirus, there is no scientific evidence to prove when and for how long an individual might become immune to COVID-19. Hence, it is advisable for physicians and lab technicians to evaluate the studies from samples and arrive at well-defined testing plans in order to improve future test results.

Getting the right COVID test

There is not a single testing approach designed to meet all needs. For every specific purpose, a specific test needs to be conducted. Choosing the right test depends on the purpose such as confirming an active COVID infection, identifying asymptomatic or pre-symptomatic cases who might be harbouring and/or spreading the virus. The best approach is to consult your healthcare practitioner and only then progress for COVID-19 diagnostic test. Above all, the best that a suspected COVID-19 patient should do is to isolate himself and avoid transmission of the virus.



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