Now that we are heading towards two years of living with Covid-19, most are familiar with testing and vaccinations. The subject of testing can be somewhat confusing though, as there are two main types of tests used in most cases right now. Whereas PCR tests are used to test whether people have actual symptoms, rapid antigen tests, often referred to as lateral flow tests, are used to test people who have been in contact with individuals who have symptoms or have had positive PCR test results.
Even if you know the above, you may still wonder how useful or, in other words, effective, rapid antigen or lateral flow tests are. That is what we are going to discuss in the following post.
What are Rapid Antigen Tests?
To start things off let’s look a bit closer at what antigen tests are, before discussing their efficiency. Whereas PCR tests are designed to detect the presence of coronavirus genetic material, antigen tests are designed to help search for specific molecules that are found on the surface of the virus. Similarly to PCR tests, they normally involve a nasal and throat swab sample, but the thing that makes them different is that they can provide a result within 15 minutes and do not need to be sent away to a lab.
Although that sounds like a major advantage compared to the wait you have when you need to send off your PCR test swab sample to get a result from the lab, as you would imagine they are not as accurate.
Are Rapid Antigen Tests Accurate and Why?
As we have said, and you may have already experienced this if you have had an antigen test, rapid covid-19 tests are quick at providing results. However, they are not always as accurate. Why?
For antigen tests to produce a positive covid-19 result, there needs to be more of the virus present in the sample. This means that rapid tests have a higher risk of producing a false negative result.
For the uninitiated, a false negative result means the test you took shows you are clear of covid-19 when you aren’t.
What Are the Chances of Getting a False Negative Result from Rapid Antigen Tests?
This is where it gets tricky, as the accuracy of tests varies for a number of reasons. Let’s look at some of the findings of research conducted to give a clearer understanding of how likely false negative results are in two different types of people, those with and those without covid-19 symptoms.
Accuracy of Test Results In People With Symptoms
According to recent research conducted, for people who are experiencing symptoms of the virus, antigen tests produced a positive result around 72% of the time.
Accuracy of Test Results In People without Symptoms
For people that do not have symptoms, it was discovered in the same research that correct positive results were only found 58.1% of the time.
Accuracy of Tests Taken During the First Week of Symptoms Compared to Second Week of Symptoms
Another area that was looked at was the difference in the accuracy of testing during the first week of experiencing symptoms compared with the second week. Rapid tests were shown to be more accurate at producing a positive result when taken during the first week.
Why Are They Still Used as Standard Tests?
As there seem to be issues with how accurate they actually are, this is a very valid question. The answers are simple though, rapid tests are quicker at providing results, more accessible and portable, less expensive and don’t require a lab or specialist.
The thought is that even though they won’t catch all cases, they can often catch the cases that may have otherwise gone undetected and are excellent for testing large numbers of people at a time. They are used in crowded, public areas, festivals, sports events, and airports often for that very reason. Besides, if you have had a rapid antigen test and are worried about the accuracy of the test or have received a negative result but experience symptoms, you can always take another more accurate form of testing, such as a PCR test.