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CommunityLabWhat is the Difference between a COVID-19 PCR Test and a Rapid Antigen Test?

August 9, 2021
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Figuring out if you have COVID-19 can be a challenge, especially since the CDC states that your symptoms may not appear until 2-14 days after your exposure to the virus. On top of that, the fevers, coughs, and chills associated with the disease are common to many viruses.

That’s why so many people are now seeking a fast, reliable way to find out if they have SARS-CoV-2, which is the virus that causes COVID-19.

Testing is being used in a variety of situations to help stop the spread of the disease, such as after exposure to someone who has tested positive, prior to traveling, or before returning to work or other organizational activities. It can help you understand if you need to quarantine and seek medical treatment, or if you’re free and clear to resume your normal lifestyle.

Let’s take a look at the main types of tests currently being used to determine whether or not you have SARS-CoV-2 and the key differences between them.

Understanding Your COVID-19 Testing Options

Diagnostic tests tell you if you currently have the COVID-19 virus, and they fall into two main categories: molecular tests and antigen tests. The difference between the two is that molecular tests check for viral molecular material and antigen tests check for viral proteins.

For SARS-CoV-2, the most widely used molecular tests are PCR (polymerase chain reaction) tests. Rapid antigen tests lead the second category. There are six key points you can look out for when you’re choosing between these two types of tests:

  • The accuracy of the results
  • The ease of testing
  • How long it takes to get your results
  • The cost of the test
  • If the test requires a second round of testing
  • If the test is FDA-authorized for travel

CommunityLab Tip: COVID-19 antibody tests are a third type of testing, but they cannot determine if you have an active COVID-19 infection because antibodies can take weeks to develop in your body.

Now let’s take a look at just what Rapid Antigen and PCR tests are, as well as the pros and cons of each.

What is a Rapid Antigen Test?

Rapid antigen tests (sometimes just called ‘rapid tests’) locate key proteins that are found on the surface of the COVID-19 virus. They are fast, simple tests that utilize a sample collected by swabbing your nose, throat, or both (known as a nasopharyngeal swab). You can typically get the results from these tests right away without the need for any specialized lab analysis.

For this reason, COVID-19 rapid tests are also called point-of-care tests, and can be easily collected and evaluated using at-home kits or at your local clinic, hospital, pharmacy, health care facility, or even at airports. They’re a relatively low-cost option because they skip the need for a high-tech lab evaluation.

One key disadvantage of rapid antigen tests is that the CDC may require a second round of testing using a PCR test if your Rapid Antigen Test comes back negative and you are:

  • symptomatic (have symptoms of COVID-19) or
  • asymptomatic (show no symptoms) and have been exposed to someone with the virus.

This second round of ‘confirmation testing’ can add significantly to the cost of rapid tests.

How Long Do Rapid COVID-19 Tests Take?

Rapid test results are quick, with results in as few as 15 minutes, although some test results may take up to 24 hours.

Are Rapid Tests Accurate?

The major downside of rapid antigen tests is that they aren’t very sensitive and tend to reveal the SARS-CoV-2 virus only when its proteins are highly concentrated. This is typically the stage at which you’re already showing symptoms and can spread the disease.

If you use this test, you have a significant chance of getting a false negative COVID-19 result, meaning the results can indicate that you don’t have the COVID-19 virus when in fact you actually do.

For this reason, only a few rapid antigen tests have FDA Emergency Use Authorization (EUA) for travel, and just a small percentage of countries accept COVID-19 antigen tests for entry.

What’s a PCR Test for COVID-19?

PCR tests are sometimes called ‘RT-PCR’ tests because they use a process known as ‘reverse transcription’ to determine if RNA nucleic acid that’s found in the COVID-19 virus is also present in your body. This lets the laboratory staff who must evaluate the tests know if you’re positive for SARS-CoV-2.

A plus to using PCR tests is that saliva can be used for the testing sample in some cases, which is considered more comfortable to collect than the traditional nose and throat swabs. Conventional nasopharyngeal swab testing is also available with PCR tests.

PCR tests also have FDA EUA for travel, and they are much more widely accepted than rapid antigen tests by countries around the globe. As we’ll see in a moment, lab-evaluated PCR tests are considered the ‘gold standard’ of testing accuracy, and therefore don’t typically require any secondary tests regardless of whether you are symptomatic or asymptomatic.

How Accurate are PCR Tests?

The Gold Star Standard

One major advantage of PCR tests is their ability to detect the virus before you become infectious to other people. Additionally, PCR tests have very high accuracy rates for COVID-19, with recent research revealing a sensitivity (positive test result accuracy) rate of more than 94% and a specificity (negative test result accuracy) rate of 100%.

How Long Do PCR Tests Take?

With common PCR tests, it can take between 48-72 hours or longer to get your results, and they can be pricier than antigen tests due to the longer evaluation times and higher-level training requirements of the staff.

The great news is that SalivaDirect™ rapid-result PCR tests (rRT-PCR) were recently developed by Yale University, with results available in just 24 hours. Costs for these rapid PCR tests are typically lower than common PCR tests since evaluation and staff training times are much shorter.

PCR Test vs Antigen Test: The Final Results

Table comparing COVID-19 PCR Test and Rapid Antigen Test

Winner for Accuracy

PCR Tests with 94% sensitivity and 100% specificity.

Winner for Ease of Testing

SalivaDirect™ PCR tests don’t require a swab, making them the most comfortable – and easiest on the environment!

Winner for Fastest Results

Rapid antigen testing is still the fastest, although the newer rapid RT-PCR tests are now a close second with 24-hour turnaround time.

Winner for Cost

It’s a tie – between the newer rapid PCR tests and the common rapid antigen tests.

Winner for Confirmation Testing

Lab-evaluated PCR tests don’t require any confirmation test like rapid antigen tests sometimes do and are themselves so accurate that they’re used as the confirmation test.

Winner for FDA-authorization

PCR tests have Emergency Use Authorization for travel and are accepted by the most countries around the world.

CommunityLab is the first lab in North Carolina authorized to use the SalivaDirect™ rapid-result PCR testing. We offer results for your rapid PCR COVID-19 test within 24 hours.

You can order your at-home saliva collection kit for the PCR COVID-19 test at www.communitylab.io or, if you are in the Asheville, NC area, visit our drive-up site in Arden, NC for either saliva or nasopharyngeal testing.  Register at www.communitylabwnc.com to get started today!