With reports of COVID-19 variants weakening the effectiveness of vaccines, the unknown duration of vaccine efficacy , and a notable segment of the population who don’t want to receive the vaccine, testing for COVID-19 is likely to remain an essential part of our routines for some time.
There are two types of COVID diagnostic tests: polymerase chain reaction (PCR) tests and antigen tests, and both can detect current coronavirus infections. The problem, however, is many people do not know the differences between the two including how they work, or when and for whom they should be used.
So, if you’ve found yourself Googling “difference between antigen and PCR test,” stop what you’re doing and read this overview we’ve put together using guidance from the Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC).
What Do They Detect?
PCR: Molecular (PCR) tests are looking to detect the genetic material inside a SARS-CoV-2 virus particle that causes COVID-19.
Antigen: Antigen tests, on the other hand, detect proteins — otherwise known as antigens — from the surface of the virus particles in people infected with the coronavirus.
How Effective Are They?
PCR: This is considered the “gold standard” of COVID-19 testing. These tests will detect even very low amounts of the virus, so are very effective at detecting people in the early stages of infection. In fact, these tests can be so accurate that they actually continue to pick up traces of the virus (so-called fragments) even when a person is no longer contagious. This can create some problems in the interpretation of test results in the late stages of infection.
Antigen: These tests are generally less accurate than PCR tests (except for some newer generation assays that are coming to market), but are effective at detecting higher levels of the virus inside the body. Therefore, if someone is in the early stages of infection, it’s possible that an antigen test may not detect traces of the virus, whereas a PCR test could.
How Do They Work?
PCR: PCR tests work using a technique called a polymerase chain reaction, which uses a machine to run a series of reactions that convert RNA into DNA, and then make millions of copies of the DNA to magnify it and test it.
Antigen: Antigen tests work by mixing the test with a solution that breaks open the virus, freeing specific proteins. For simple strip-based antigen tests, the method is similar to the one used in pregnancy tests. The more recent, sophisticated antigen test that AllClear uses utilizes microfluidics — very small channels in which chemical reactions occur — and more complex methods to detect the proteins, such as immunofluorescence, creating accuracies that are closer to those of a PCR test.
How Are They Administered?
PCR: PCR tests are administered via nasal swabs or saliva samples.
Antigen: Antigen tests are administered by carrying out either a nasal swab, nasopharyngeal swab, or oropharyngeal swab, which obtain secretions from the back of the throat or the nose.
Here at AllClear Healthcare, our rapid, on-site PCR test is conducted using painless saliva samples, whereas our antigen test is administered using a nasal swab.
How Long is the Turnaround Time?
PCR: Traditional laboratory PCR tests can take 4-6 hours after receipt of the sample in the lab, sometimes up to 24 hours to process, leading to turnaround times averaging 1-2 days. Here at AllClear Healthcare, our on-site PCR test runtime is under 20 minutes and offers the same levels of accuracy as a lab-based test.
Antigen: There is a wide range of antigen tests on the market, most of which return results in 15 minutes. The runtime of our highly-sensitive antigen test, which delivers results that resemble the accuracy of a PCR test, is just 12 minutes.
AllClear COVID-19 Testing Pros and Cons
To summarize antigen versus PCR testing for COVID-19:
Deciding Which Test to Choose
When it comes to deciding which COVID-19 test is best for you, there are several factors to weigh.
If you’re getting tested to travel or attend a one-off event with people in high-risk groups, then PCR tests could be a better option to provide immediate surveillance.
Whereas if you’re a business looking to regularly test hundreds of employees in order to bring them back to the workplace, rapid antigen tests may be a more suitable option as they will be carried out more frequently, providing more reliable results.
Are you looking for a rapid, accurate, and affordable COVID-19 testing service for yourself or your business? Contact us to find out more today.
Once you’ve determined the difference between PCR and antigen tests, take your results seriously. If you test positive, find out what steps you should take and self-isolate for at least 10 days since the date of your test. If you test negative, continue to follow measures to protect yourself and others, such as masking, social distancing, and avoiding crowds.