COVID-19 IgM/IgG Rapid Test vs. RT-PCR: A Comparison Between Two Methods
As the number of confirmed COVID-19 infections worldwide reached 5.6 million, with 2,430,603 recoveries and 352,225 deaths as of May 27, the World Health Organization continues to ask for immediate action in testing all individuals suspected with COVID-19.
WHO notes that the foundation of an effective pandemic response is the capacity to conduct mass-scale testing. The Director-General of the World Health Organization, Dr. Tedros Adhanom Ghebreyesus, said that all countries should prioritize testing for the virus. He also pointed out the pressing need to ramp up contact tracing efforts and isolation of infected individuals.
There are two primary types of testing methods currently in use today. The first test is called the IgM/IgG Rapid Test, while the second one is called the polymerase chain reaction test (RT-PCR). Below are several characteristics that set the two tests apart.
IgM/IgG Rapid Test Kits
The IgM/IgG Rapid Test Kit produces fast results. However, rather than identifying the genetic materials making up the novel coronavirus, the IgM/IgG Rapid Test detects the presence of antibodies in a person’s system.
So how exactly is this test used? First, licensed medical professionals must extract blood from a probable COVID-19 patient. Then, they load the sample to the test kit, along with three drops of sample diluent. After fifteen minutes, the kit will generate a result, and the licensed professional can interpret it.
Generally, the test kit reads for two different types of antibodies: the immunoglobulin G(IgG), which is the delayed immune response, and the immunoglobulin M (IgM), or the early immune response.
IgM antibodies are found in individuals who are SARS-COV-2 positive, while the IgG antibody is seen in patients who recovered from the infection. For instance, you might show no symptoms of the COVID-19 disease yet still test positive for IgG antibodies in your system. This might mean that you have been previously infected and generating immunity from the virus. In this case, you need to self-isolate.
However, if you are positive for both antibodies despite showing no symptoms, you must self-isolate for fourteen days before taking another IgM/IgG rapid test. If you test negative for IgG and positive for IgM without any symptoms, it means that you are infected. When this happens, it is best to take an RT-PCR test to confirm.
Moreover, if you test negative for both antibodies while showing no symptoms, your probability of infection is unlikely. To be safe and sure, consider taking another antibody test after seven days.
Although IgM/IgG rapid testing kits produce quick results, the test’s preciseness still depends on the sensitivity of the testing kit itself. Therefore, there is a high chance of errors in the results. False negatives and false positives are common with this type of testing kit.
Antibodies only progress a few weeks after the infection. For this reason, rapid coronavirus test kits may miss it in the earliest phases of the disease. A confirmatory RT-PCR test is needed to be performed on those who got a positive result in the rapid test.
RT-PCR Testing
The Polymerase Chain Reaction (PCR) is a common technique that has been used for about thirty years in medicine and research to identify genetic information. A special and improved version of the PCR is the reverse-transcription Polymerase Chain Reaction (RT-PCR).
The RT-PCR test was first used to detect ribonucleic acid (RNA) strands. Today, however, it is used to identify SARS-CoV-2, the virus causing the COVID-19 disease. Since RT-PCR directly tests for the presence of the virus, it became the leading test to detect infection.
RT-PCR tests are reliable and sensitive and can produce accurate results within three to four hours. However, it will take more hours if the samples are needed to be sent to an external laboratory.
You might be asking, ‘how does this type of testing method work?’ Well, first, licensed medical workers will collect samples from a suspected COVID-19 patient. Chemicals will be used to get rid of fats, proteins, and other molecules, thus, leaving RNA strands behind.
The strands will be a combination of a person’s genetic material and the viral RNA that may be present in the system. The RT-PCR copies the RNA to DNA and is increased in size to detect viruses through a PCR machine.
Moreover, fluorescent markers are usually used to secure the amplified DNA and supply light. If the light’s intensity within the sample hits a certain threshold, then it means the sample tested positive. Otherwise, the result is deemed negative.
It’s important to remember that RT-PCR testing won’t be able to identify if an individual had contracted the virus and recovered from it. It only detects an active infection present in a person’s system.
Takeaway
Not all COVID-19 test kits are alike, with each having its own set of advantages and disadvantages. Despite the different methods each one uses, these kits are still necessary to fight the spread of the virus. However, there’s currently a shortage of test kits available. Hence, a hierarchy must be heeded when it comes to the priority of testing and which method to use.
About the author: Cassie Wilson is a freelance journalist and author with a 30-year background in health and medical reporting. Her site is at www.cassieworks.com. Previously, Cassie worked in public relations and corporate communications at The Johns Hopkins Medical Institutions as assistant director of public affairs. Concurrently, she served as director of Health NewsFeed, a daily radio feature heard on more than 400 stations in the U.S. and Canada.
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Tom O
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Interesting. If you test positive to the antibody test, the author says, but have no symptoms, you must self -isolate… and I say Why? According to WHO, a person that has no symptoms rarely passes on the virus. Besides, giving the gift of the virus to a healthy person is doing the world a favor, thus reducing the need of “vaccines.”
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Charles Higley
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They want the public to be scared of everyone by making the rare asymptomatic carrier a common thing, because the public does not know better. Typhoid Mary was famous for her rare condition, not a common condition. The WHO person who admitted carriers were rare was forced to walk that back within hours because without these many carriers they could not justify the lockdowns, destroying our economy, and the continuing abuse we are suffering via masks (the face burka) and other useless regulations.
A elderly lady in a retirement home here was confined to her room for two months to protect her from these imagined threat carriers. Last week management started letting her out in the garden alone for 15 minutes each day. Maximum security prisons give an inmate an hour a day. She is paying for this abuse? Wow.
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Finn McCool
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Oh dear. This is perhaps one of the most fatuous articles on disease testing I have seen to date. The last paragraph says it all. ‘….fight the spread of the virus’.
“As of 9am on 16 June, there have been 6,981,493 tests, with 113,107 tests on 15 June.
298,136 people have tested positive.”
https://www.gov.uk/guidance/coronavirus-covid-19-information-for-the-public
That amounts to a prevalence of 4.2% Now the sample size is biased due to the number of health care workers and actual patients (2.2 Million), but a bit of Bayes will show the probability of testing positive and actually being infected is ~52% (Assuming 96% specificity and sensitivity.)
Maybe the author should pick a fight with someone her own size.
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Charles Higley
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“Today, however, it is used to identify SARS-CoV-2, the virus causing the COVID-19 disease. Since RT-PCR directly tests for the presence of the virus, it became the leading test to detect infection.”
This is hooey. There is no Gold Standard Covid-19 culture to test this test against. And the test has to be shown to be specific when C-19 is present even when other coronaviruses (covis) are present. That work has never been done. Furthermore, as the flu season is a salad of influenza and covis, no one has ever sorted out all the viruses a critical patient might have. There is no proof that Covid-19 is the lethal culprit. Patients can have multiple viruses at the same time and it is ingenuous to think that, just because you think you have a test for a specific virus, that it is the culprit because the test said it was present. It’s just wrong to assume that. Yes, there is a covi out there that can kill the elderly/compromised, but there is no proof at all that C-19 is guilty.
As the original PCR test was developed by the Chinese using lung perfusates and they simply assumed the RNA in the clear, centrifuged fluid contained ONLY the virus, the test they created was bogus and only tests for covis in general. It has been admitted more than once that the PCR test only tests for a general covi sequence, which explains why there is 80% false positives, because covis are environmental and we get them off and on all year round. Go up to the Arctic and test the Inuit and some will test positive despite no contact with the outside world.
The crap-level of the tests also explain why we have so many positive asymptomatic people. Assuming that the test is valid, they conclude that these people are carriers when, in the real world, they would be called false positives. But, no, the thick-headed powers-that-be assume a positive is a “case.” In the real world, you are not a case if you are not ill or have no symptoms, duh. But, pretending that 25% of the population are asymptomatic carriers is a good way keep the public fearful of everybody. Wow. We are now all in first grade and everybody has Cooties. What utter bunk.
I would never get either test as they are based on the same crappy science. No one has the Gold Standard on which to design a test and no one has done any tests for interference by other viruses. Really bad science. There is a good reason the US Navy will not use the PCR test—too many false positives.
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Bob D.
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A few months ago I brought up a SARS-CoV-2 RT PCR test manufacturer website. In red letters near the top, it said “for research purposes only. Not for diagnosis.” A reason for this was listed below: this test may react positively to other Covid viruses and non Covid viruses.
It is crucial to test any test for accuracy. This requires an unambiguous gold standard. The lack of a gold standard for any Covid 19 test would make false positive and false negative assessment impossible. And If the CDC and other agencies are correct that most people who test positive to Covid 19 will have no or mild symptoms, then there is the question, is the illness/death of the patient due to Covid 19 or is it being a harmless “passenger” virus.
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tom0mason
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“As the number of confirmed COVID-19 infections worldwide reached 5.6 million, with 2,430,603 recoveries and 352,225 deaths as of May 27, the World Health Organization continues to ask for immediate action in testing all individuals suspected with COVID-19. “
If these numbers are anywhere near correct then the mortality rate (number of deaths/total number infected) is truly minute — around 0.63% — closer to 1 in 200 than 1 in 100. So lets all panic!
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Colin Henderson
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This article should be withdrawn it is full of misinformation and very misleading. See Charle Higley’s comments.
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