Coronaviruses are in fact a diverse family of viruses. Coronaviruses have spiky projections on its surface that look like crowns, hence the name “corona”. The greatest amount of coronavirus diversity is seen in bats, but some also reside in humans. Most of the time they cause mild respiratory illnesses, like the common cold. However, some type of coronavirus can cause severe diseases like COVID-19, the respiratory disease that the world is now confronted with.
COVID-19 is the official short name for Corona Virus Disease 2019. COVID-19 is caused by the SARS CoV-2 virus, a Coronavirus, that causes severe respiratory illness. SARS stands for Severe Acute Respiratory Syndrome, a severe condition to the lungs. SARS CoV-2 is a new type of Coronavirus and first identified in Wuhan in December 2019. It is a genetic relative of the SARS CoV virus, which was first identified in 2003. Like the SARS CoV virus of 2003 and the MERS CoV virus that emerged in 2012, the SARS-CoV-2 virus, i.e. the Coronavirus that causes COVID-19, is caused by an animal Coronavirus which was transmitted to humans. This is called “zoonotic transmission”.
The PCR-test, antigen test and the antibody test are three different types of tests. The PCR- and the antigen test both look for the virus with different techniques. The antibody test looks for your body’s reaction to the virus in terms of antibodies.
A PCR test looks for the genetic material (the RNA, or ribonucleic acid) of the virus and uses an amplifying technique, the so-called polymerase chain reaction (PCR) technique. As a result, the test is able to find miniscule amounts of SARS-CoV-2 virus particles. Test results are obtained through the use of laboratory equipment and it usually takes 24 to 48 hours before results come out. PCR tests are almost 100% accurate in determining the presence of an infection. However, since a PCR-test will locate a virus infection already with a tiny number of virus particles, does a positive test result not always mean that you are also infectious. To determine whether you are infectious to others, it could be useful to take an antigen test.
The antigen test is a rapid test. The antigen test detects the proteins, so-called “antigens”, that are located on the surface of the SARS-CoV-2 virus particles. Within 15-20 minutes the test will determine whether those antigens are present in your nasal or throat mucus, which presence will indicate an active virus infection. The antigen test identifies people at the height of the infection, when there are many virus particles in the body. Therefore, it is best to take the antigen test in the first two to nine days after symptoms started. At this stage the number of virus particles of a SARS-CoV-2 infection are usually the highest. This is also the phase when someone is the most infectious.
A positive result from an antigen test is a clear indication that the tested person is infected with the SARS-CoV-2 virus and also that he or she is infectious to other people. A negative result means that the tested person is most likely not infectious. It does, however, not necessarily mean that the tested person is not infected.
The antibody test, finally, is not looking for the SARS-CoV-2 virus itself, but traces the presence of antibodies in the blood. Antibodies are being produced by the body in reaction to the virus. First, the body creates IgM antibodies; antibodies that are released by your immune system as an initial defence reaction against infections. About 15-20 days after symptoms first appear, long-term IgG antibodies can be found in the blood of most people who have been infected. These are the antibodies that the body retains so it can fight off follow up attacks by the SARS CoV-2 virus. IgG antibodies give a person a form of immunity. The antibody test detects both IgM and IgG antibodies in the blood.
Tests should be stored at 4 °C – 30 °C, be kept dry and away from sun light. The shelf life of the tests is 12 months. Each test card/test strip should be used within 1 hour after unsealing. Production date and expiration date are shown on the package label.
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A rapid antibody test is a diagnostic test, a qualitative (i.e. positive or negative) lateral flow assay that is small, portable, and can be used at point of care. These tests often use blood samples from a finger prick, serum or plasma samples. A COVID-19 rapid antibody test can tell the presence or absence of antibodies against the virus present in patient fluid, however, rapid antibody tests will not indicate the quantifiable amount of antibodies in the patient serum, and therefore cannot tell you whether these antibodies are able to protect against future infection. Also, not all rapid antibody tests test for both patient IgG and IgM antibodies, which is an important marker to indicate at what stage of the disease you might be in.
The product is based on the antigen-antibody reaction and immunoassay technique. The test device contains colloidal gold labelled SARS-CoV-2 recombinant protein, mouse anti-human IgG antibody immobilized in test
area G, mouse anti-human IgM antibody immobilized in test area M and the corresponding antibody in quality control area (C). During the test, when the SARS-CoV-2 IgM or IgG antibody is at or above the detection limit of the test, the SARS-CoV-2 IgM or IgG antibody in the sample binds to the colloidal gold labelled SARS-CoV-2 recombinant protein which is pre-coated on a gold label pad. The conjugates migrate upwards through capillary effect and will be captured by mouse anti-human IgM antibody immobilized in test area M and/or subsequently by mouse anti-human IgG antibody immobilized in test area G. This produces a purple-red band which appears in the M and/or G test area.
Regardless of the presence or absence of the SARS-CoV-2 antibody in the sample, a purple-red band will appear in the quality control area C. This is a criterion for judging whether there is enough sample and whether the chromatography process is normal. It also serves as the internal control standard for reagents.
IgM are the antibodies released by your immune system as an initial defence reaction against infections, in this case the SARS CoV-2 virus, i.e. the virus strain that causes Coronavirus disease 2019 (COVID-19). The presence of IgM antibodies in your blood indicate an active or recent infection. The IgG are long-term antibodies which have immunological memory. This type of antibody that the body develops in response to the infection is more specific to the virus. The body retains the IgG antibodies so that it can fight off follow up attacks by the SARS CoV-2 virus. Often, the IgG has a life time existence. In certain cases, however, this might not apply. For group immunity to happen, the IgG antibodies play a vital role as most IgG carriers are non-transmitting.
No, an IgM positive test simply indicates that your body has released a first line of defence against the coronavirus that causes COVID-19. An IgM positive test, however, does not mean that your body has immunity. IgG antibodies, on the other hand, do provide a higher degree of immunity, though, unfortunately, we do not know how yet long IgG antibodies to SARS-CoV-2 will remain present in the body after the infection has been cleared.
If you have an IgM or IgG positive test or both IgM and IgG, the test result is positive. With a positive test, it is recommended to carry out a second test. A second test carried out with the same result assures you that the test result is 99,95% accurate.
If positive, contact your GP. The result of the test should be comprehensively judged by a physician in combination with other clinical information. This test should not be used as the only criterion. A positive test results implies that your body has been in contact with the Coronavirus in the recent past. Isolate yourself from others to keep infection risk as low as possible.
Until the vaccine against this type of Coronavirus is available, it is advised to repeat the test every few weeks. This is because, even if the test result is negative (i.e. the test indicates that there are neither IgG nor IgM antibodies present in your blood), the Coronavirus could be incubating for up until 14 days before it triggers the IgM response in your body. Taking the test regularly will improve certainty about your current health status.
A PCR, or Polymerase Chain Reaction, test, is usually done in the hospital. With a cotton swab, a caretaker will go deep into the nostrils to take a sample of your sputum. Two samples will be taken, one from deep inside the nose, and one from the inside of the mouth. If the Coronavirus (SARS CoV-2) is incubating in your body, parts of the virus (the RNA (ribonucleic acid) genetic material) will be present in the sputum. The samples will be sent to a lab, where a PCR-detection machine will be able to detect the virus with the help of spectrum light. Although a PCR-test can very accurately indicate the presence of viral material during infection, i.e. the incubation stage of the virus, it will not be able to confirm whether you have COVID-19, the disease which is often the result of infection with the SARS CoV-2 virus. It will also not indicate if a person was infected and subsequently recovered. Whether you have or had COVID-19 can only be confirmed with a blood test.
Blood-based tests are serology tests that can be used to identify whether people have been exposed to a particular pathogen by looking at their immune response. After the incubation period, a person infected with the SARS CoV-2 Coronavirus will show symptoms of the virus. Simultaneously, while the infection is taking shape, your body will produce antibodies to fight the virus. Based on the antibodies your body is producing when confronted with the Coronavirus, a blood test can tell whether the virus is present in your blood. Not all blood tests are accurate though, so it is very important to use a test which is both accurate and can tell you at what stage of the disease you are.
The Geneses Medical rapid test is one of very few blood tests currently available to be able to indicate the presence of IgM-antibodies, which are the measurement for the stage of infectiousness of the virus, as well as the presence of IgG-antibodies, which is the measurement for immunity against the virus. The test can also indicate whether there is a combination of the two, when there are both IgM-antibodies and IgG-antibodies in your blood, which means the virus is still virulent in your body but immunity is also being built up.
COVID-19 blood tests are an important indicator of the prevalence of the disease in a population by identifying individuals who have developed antibodies to the virus, including people who may have had an asymptomatic response or have recovered.
The COVID-19 Rapid Antibody Test of Geneses Medical (manufactured by Lepu Medical Technology) gives an accuracy of 99,3%, which is measured by the sensitivity and specificity for both IgM and IgG antibodies. The sensitivity and specificity on IgM and IgG antibodies of our COVID-19 Rapid Antibody Test are as follows:
Sensitivity = coincidence rate of negative = true positive rate = 100% Specificity = coincidence rate of positive = true negative rate = 99.2%
Sensitivity = coincidence rate of negative = true positive rate = 97.2%
Specificity = coincidence rate of positive = = true negative rate = 100%
Combined this gives an average accuracy of 99,3%. Accuracy indicates the proportion of the actual positives and actual negatives that are correctly identified by the test. This is measured by the percentage of correct classifications. The accuracy is calculated by the weighted average of the true positives and true negatives identified by the test divided by the total test sample for IgG and IgM on sensitivity and specificity.
|Geneses Medical (Lepu Medical)||IgG||100,0%||99,22%||99,55%|
Source: Clinical Validation on IVD kits, Lepu Medical, 2020-02
Before taking a test, it is important to check the sensitivity and specificity of the test. Sensitivity measures the positive accuracy of the test, while specificity measures the negative accuracy of the test.
What does sensitivity and specificity mean?
Sensitivity measures correct positive results; in other words, it will correctly identify the people who have the disease. For example, if a COVID-19 test is 97% sensitive, it will correctly identify 97% of the people who have been infected with the SARS-CoV-2 virus - called a “true positive”. However, this also means that 3% of the people who are infected and got tested would get a false negative result - they do have the virus, but the test says they don’t.
Equally important is the specificity of the test. Specificity measures correct negative results; in other words, it will accurately identify the people who do not have the disease. So, if a COVID-19 test is 97% specific, it will correctly identify 97% of the people who have not been infected with the SARS-CoV-2 virus – registering a “true negative”. However, this also means that 3% of the people who have not been infected will test positive for the virus and receive a false positive result. So, to determine whether a medical test is ‘accurate’, look at the sensitivity and specificity measurements of the test in the validation report.
Sensitivity indicates the proportion of the actual positives that are correctly identified by the test. It is measured by the percentage of people who are correctly identified as infected by SARS-CoV-2.
Specificity indicates the proportion of actual negatives that are correctly identified by the test. This is measured by the percentage of healthy people who are correctly identified as not infected by SARS-CoV-2.
The COVID-19 Rapid Antibody Test of Geneses Medical (manufactured by Lepu Medical Technology) gives an accuracy of 99,3%, measured by the sensitivity and specificity for both IgM and IgG antibodies.
Underneath table shows the sensitivity and specificity of values (IgG + IgM) and accuracy of five SARS-CoV-2 antibody tests.
|Sensing Self *||87,50%||96,75%||94,62%|
|Abbott Base point *||86,43%||99,57%||91,61%|
|Lepu Medical (Geneses Medical)||98,79%||99,64%||99,32%|
|Aytu Bioscience **||91,96%||100,00%||
* Information For Use (IFU) of test kits
** John Hopkins website (https://www.centerforhealthsecurity.org/resources/COVID-19/serology/Serology-based-tests-for-COVID-19.html)
» Download de White Paper Comparison SARS-COV-2
It can be confusing when someone has a positive PCR test result, then performs an antibody test and the result is negative. A negative test result from the antibody test, when only quality control line C appears, indicates that the test could not detect a sufficiently measurable amount of antibodies in the blood sample. First of all, the moment the test was taken is important. It takes a while before the body has produced sufficient antibodies to fight off the SARS-CoV-2 virus. In general, it will take 10 days after first symptoms appeared that antibodies can be found in the blood. If someone takes an antibody test before that time it could well be that the test was taken 'too early' and therefore no measurable amount of antibodies could be detected. In this case, we recommend to repeat the test after 7-10 days.
The first antibodies that could be found in the blood are the IgM antibodies: these antibodies will be released by the body's immune system as a first immunity response to the infection. Approximately 15-20 days after first symptoms appeared most people will also have IgG antibodies in their blood. The IgG antibodies will provide you with a form of immunity to the virus. The exact moment IgG antibodies appear differs form person to person though. Also note that research has shown that the IgG antibodies might disappear after some time.
This being said, it is possible that someone with a positive PCR test result will have a negative antibody test result (where only the quality control line C appears) while the test was not taken too early. This could be an indication that the body has not produced sufficient antibodies in spite of the virus infection. A possible explanation could be that the infection was very mild or even a-symptomatic (which means that there were no symptoms), due to which only very few antibodies were created. There is, however, no simple, univocal explanation. If this is the case for you, please contact your doctor. It does mean that your body has not built up immunity to the disease and that you have to stay alert not to be infected again.
If, after taking the test, the display on the test kit remains blank (control line C does not appear), this might be due to the amount of liquid that has been used. In order for the blood to ascend an ample amount of fluid should be used. We recommend three full drops of buffer fluid. So, when taking the test, make sure you use sufficient buffer fluid. You can empty the whole ampoule if needed, the amount of fluid in the ampoule is enough for the test to work.
The antigen test detects proteins that are located on the surface of the SARS-CoV-2 virus (so-called “antigens”). The test is performed by testing samples collected from the nasal cavity. SARS-Cov- 2 virus is known for nesting and multiplying in the mucosal tissue deep inside the nasal cavity during the first week after symptoms appeared. During this first week, the viral load will be the highest, after which the virus will spread to the lower respiratory tract and the lungs. This is where the virus causes the disease COVID-19.
An antigen test is a rapid test which is able to detect the SARS-CoV-2 virus with people with a high(er) viral load. These are the people who are also, at the moment of testing, potentially the most infectious. The test is most effective in the first two to nine days after symptoms appeared, this is when the viral load in the upper respiratory tract is the highest. In this phase we speak of an active infection. After taking the nasal sample from deep inside the nose the test can determine whether the proteins of the SARS-CoV-2 virus are present in a person.
A positive test result indicates that that particles of the virus have been found in the nasal mucus. This means that you are not only infected with the SARS-CoV-2 virus but also that you are infectious to other people. A negative test result indicates that you are most likely not infectious. However, it does not necessarily mean that you are not infected. There could be a very low viral load in the body that cannot be detected by the antigen test, because you are not (yet) at the peak of the infection.
The antigen test is very reliable, but there are a few things that you have to keep in mind. First of all, it is very important that the test is performed correctly. This means at first that the nasal sample should be taken from deep inside the nasal cavity, from against the back wall of the nasopharynx. This is primarily where the virus nests and multiplies in the first week after symptoms appear. It is very important that the nasal sample is well saturated with the buffer fluid, so that the intended reaction in the test kit can take place.
Secondly, the time that the antigen test is being taken is important. If you have only very recently been infected or had corona-related symptoms already more than two weeks ago, then you will probably have a relatively low viral load in your body. Chances are that the antigen test will not be able to pick this up as the antigen test works best in the first two to nine days after symptoms first appeared, the phase when the viral load is the highest. If in this case, you have a negative test result, you are recommended to also take a PCR-test or, if complaints took place some time ago, an antibody test.
The antigen test is, in the first place, a very good indicator of infectiousness. If the test has been performed properly and the test result is negative, then the tested person is most likely not infectious to others. Please note, this does not necessarily mean that the tested person is at the moment of testing not infected. Therefore, if you experience corona-related symptoms but you have a negative test result, we recommend that you do an additional PCR-test to be sure.
The Lepu Antigen Rapid Test uses the colloidal gold immunochromatography technique, which assures a high degree of accuracy, in this case a specificity of 99.2%. Specificity indicates the ability of the test to correctly identify people who do not have the disease. This means that if your test result is negative, you can be highly assured that you are not infectious.
A positive result from the antigen test is a clear indication that the tested person is infected with the SARS-CoV-2 virus, and also infectious to other people. This is because the antigen test identifies people at the height of the infection, when the viral load in the body is high. A positively tested person is likely to be in the first phase of infection after symptoms appeared. At this stage, the number of virus particles are the highest with a SARS-CoV-2 virus infection. This is also the time that somebody is most infectious. So, be careful and isolate yourself for the coming 10 days (quarantine).
A PCR-test is a very sensitive test. The test is able to detect even minuscule amounts of virus particles in nasal and throat mucus. This is because a PCR-test uses an amplifying technique, called the polymerase chain reaction (PCR). For approximately 12-24 hours the genetic material of the virus will be amplified in a lab environment, after which very sensitive lab equipment will measure the presence of the virus. As a result, even the lightest infection will be detected, also in people who did experience any symptoms. The antigen test on the other hand is mostly effective when there is a high viral load in the body.
Antigen tests and PCR-tests are two different types of tests. The antigen test does not look for the genetic material of the virus, like the PCR-test, but detects proteins that are located on the surface of the SARS-CoV-2 virus (so-called “antigens”). The antigen test is a rapid test, no amplifying technique is being used and no lab equipment is needed. As a result, a person with a very light SARS-CoV-2 infection could test positive with a PCR-test and negative with an antigen test, mainly because the viral load will not be high enough to be detected by antigen test. That being said, an infected person with a low viral load does not always have to be infectious; a person who tests positive with an antigen test on the other hand can be almost 100% certain that he or she is infectious to other people.
A second reason for having a positive PCR-test and a negative antigen test could be the moment that the test has been taken. The antigen test is most reliable if the test has been performed in the first two to nine days after symptoms appeared. At this stage the viral load is the highest and this is also the time when someone is most infectious.