Difference Between COVID-19 Tests

Published May 23, 2023

At-home tests. Throat swab. PCR. Antibodies. Test strip. These words were not part of our regular vocabulary before 2020. Now, they are commonplace as we navigate a new normal that includes testing for coronavirus.

Since the early days of the COVID-19 pandemic, testing has been critical in helping to identify cases, access treatment, and slow the spread of the virus. There are two main types of COVID tests; diagnostic tests and antibody tests. 

Now that millions of tests have been administered and the results analyzed, we’ve got more information about the difference between COVID tests, how they work, and which one is most accurate.

What Is a PCR test?

A PCR test, also known as a polymerase chain reaction test, is a diagnostic molecular test that detects the presence of the virus. Molecular tests can confirm if you are actively infected. 

PCR tests were developed several decades ago and, by 1985, had been refined to the point they could be used reliably in a laboratory setting. PCR tests were the first to be widely deployed as coronavirus spread across the United States.

How Do You Take a PCR Test?

There are a few ways to get a sample for PCR testing. The Mayo Clinic explains that samples can be taken from:

  • The back of your nose.
  • Your nostrils.
  • The back of your throat. 
  • Saliva. 

Once a sample is obtained, it is sent to a laboratory for analysis. If there are lab facilities onsite, the results may be available in minutes. Results are typically available within one to three days for tests sent to an offsite lab. 

PCR tests are considered to be the gold standard for detection and accuracy, especially when done by a trained healthcare provider. They are unlikely to produce false positives or false negative results.  

When Should You Go for a PCR COVID Test?

The Centers for Disease Control recommends a PCR test if:

  • You have symptoms.
  • It has been at least five days since you had a suspected exposure to coronavirus.
  • You will be in a high-risk setting or close contact with someone at risk for severe illness. 

There are over 15,000 sites across the United States where you can access a free PCR test. Use the online locator to find a location near you.  

What Is a Rapid Antigen Test?

Rapid tests detect viral proteins called antigens. The COVID-19 virus has several antigens that rapid tests can identify. Rapid antigen tests have a long history of being used for infectious diseases and are popular due to their low cost, simplicity, and quick turnaround time.

How Do You Take a Rapid Antigen Test?

These tests are most accurate when taken by someone who has developed COVID-19 symptoms. A sample is obtained using a nasal swab and analyzed in 15 to 30 minutes. 

Antigen tests can be less accurate than PCR tests, especially when taken by people who are asymptomatic. It is unlikely to get a false positive, but a false negative test result is possible. 

The CDC recommends a few strategies to help increase the accuracy of antigen tests. 

1. Don’t test too soon. 

The test will be more accurate if you have symptoms or wait a few days after close contact with someone who has COVID-19. 

2. Test more than once. 

If you get a negative antigen test result, consider testing again after 48 hours. If that test is negative, test again after another 48 hours have passed. If that result is negative but you suspect it is a false negative, go for a PCR test. 

3. Follow the test instructions as precisely as possible.

Obtaining an adequate sample and ensuring it is processed properly is critical. You may get inaccurate antigen test results if any part of the testing process or sample is compromised.

When Should You Take a Rapid Antigen Test?

Consider using an antigen test when you have symptoms and want results quickly. Rapid antigen tests are convenient because they can be used anywhere and don’t require going to a testing location or healthcare provider. 

Antigen tests can be taken at home and are also offered at some testing facilities. You can order free testing kits from the United States Postal service.

The United States government has approved several rapid antigen tests for use at home. They can be purchased online and found in-store at local pharmacies and grocery stores. Antigen test kits cost anywhere from $5 to over $35, depending on the brand and retailer. Your insurance provider or group health plan may cover the costs of these tests.   

PCR Testing Versus Rapid Antigen Testing

This checklist combines guidance and recommendations provided by the World Health Organization and the Centers for Disease Control, and is one tool you can use to help determine which test to take. This does not replace the counsel of a qualified healthcare provider.

If you are experiencing severe symptoms, a sudden worsening of symptoms, or have health concerns, you should seek medical attention. 

PCR test

  • You have COVID-19 symptoms.
  • You were in close contact with someone who has tested positive for COVID-19.
  • You were recently in a high-risk setting.
  • You will be in close contact with an immune-compromised person. 
  • You have been asked to provide PCR test results to attend an event or travel.
  • You can go to a Test to Treat location
  • You want accurate results after one test.
  • You are able to wait up to three days for test results. 
  • You have not had COVID-19 or a positive test result in the past 90 days.

Rapid antigen test 

  • You have COVID-19 symptoms. 
  • You have access to a rapid test kit OR you can go to a Test to Treat location.
  • You need same-day test results. 
  • You can repeat testing after 48 hours if the first result is negative.
  • You had a confirmed COVID-19 infection within the past 90 days.

Which Test Is Better At Detecting New COVID-19 Variants?

Under certain circumstances, viruses can produce mutations, and COVID-19 has mutated several times since 2020. When a virus has one or more mutations, it is called a variant. Each variant differs in symptoms, severity, transmissibility, and other factors. As viruses change, they may become harder to detect.

At this time, neither test has shown a significant advantage when it comes to detecting new variants.

The United States Food and Drug Administration reported that some variants might result in an initial false positive on both PCR and antigen tests. For anyone potentially infected by a COVID-19 variant, experts recommend repeat testing when there is a negative result on diagnostic or antigen tests. 

Today we have quick and easy access to reliable testing, compared to when the coronavirus pandemic began. There are options for free and paid tests that can be administered in person or taken at home. If you think you might have COVID-19, testing is an important step that will help you get faster access to treatment and keep others safe from infection.

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