Options for rapid testing for COVID-19
Recently, the capacity for taking a corona test at triage centers, GP waiting posts and the like has been significantly increased. Fortunately, because more positive cases can be discovered this way. Unfortunately, the downside is that the laboratories cannot keep up with this pace. They simply have too little capacity in manpower and machines. Normally, the test result for a PCR test must be delivered within 24 hours. The consequence of the large influx of requests is that people often have to wait 2, 3 days, or even longer for the test result. And in the meantime, infected people continue with their daily lives or – in the best case – they go into quarantine. The situation is also uncertain for colleagues, friends and family of someone who is awaiting the result. Therefore, faster testing methods are needed. In this blog, Alcoline tells you more about the various rapid test options.
COVID-19 antibody tests
After the outbreak of the virus, COVID-19 serological tests quickly came onto the market. These so-called rapid tests, which check in 10 to 15 minutes whether the body has produced antibody substances (IgM/IgG) in response to a virus attack, initially had a questionable reputation. Many brands underperformed, causing the Belgian government to ban them by law for six months. A lot of research has now been done, the wheat has been separated from the chaff, and there are reliable products on the market. Since September 19, 2020, the date on which the ban on the sale of these tests expired, they have been freely available.
COVID-19 antigen tests
Recently we have also seen COVID-19 Ag rapid tests appear. An antigen is the entity that causes the disease. In the case of COVID-19, the antigen is the virus itself or, more specifically, the proteins of the virus. Antibodies are immune proteins that the body produces in response to the antigen. They mark the antigen as harmful, so that the rest of the immune system can neutralize it.
Detection with different types of tests
The window of detection of the COVID-19 antigen and antibodies is different. For the antigen, the detection window is similar to that of the PCR test. Detection is possible 2 to 3 days before symptoms develop. This means that people are contagious several days before they develop the first symptoms. Some people do not develop symptoms during the infection, but test positive and are also contagious to others. The infection reaches its peak the day after symptoms appear. Antigen tests become less reliable over time as the immune system begins to clear the virus, and the virus begins to descend into the lower respiratory tract (making nose and throat swabs less effective).
The timeline of both antigen and antibodies is illustrated below.
Characteristics of an accurate corona test
An accurate corona test is both sensitive and specific. A sensitive test gives a positive result for a large proportion of people who are infected, so it gives a low rate of false negative results. A specific test gives a negative result for a large proportion of people who are not infected, so it gives a low rate of false positive results. Unfortunately, a false positive or false negative result cannot be completely ruled out. The greatest risk of error exists between days 7 and 10 after the first symptoms, when the virus has already decreased significantly and the amount of antibodies is still limited.
Conclusions
First, it is important to be careful when drawing conclusions from a test result. Several factors are important, such as the quality of the test, the correct execution of the test, but certainly also the time at which the test is administered. The second conclusion we can draw is that the antigen and antibody tests complement each other well. By using both tests you answer the question: 'Am I infected or have I had the virus, or not?' The third conclusion: a positive antigen rapid test is best interpreted by a doctor and verified with a PCR test.
Would you like to order a rapid test? You can do so here on the Alcoline website, or send a message via info@alcoline.be.
