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Trust gold-standard PCR-based COVID-19 testing to keep moving forward
Confidence in COVID-19 testing results helps free us all to focus on the great things in life. PCR-based tests are designed to enable early virus detection, even in asymptomatic cases, and help deliver reliable answers.
PCR and antigen-based testing technologies
The virus spread around the world in a few short months, and its variants continue to sweep the globe. The good news is that a robust testing program as part of an organization’s SARS-CoV-2 response can help mitigate the spread of the disease. Diagnostic testing can identify active coronavirus infection and inform proactive next steps, like quarantining, to protect the infected individual and close contacts.
As testing is critical to diagnose and contain the spread of the virus, there are multiple methodologies available to yield a coronavirus testing result. The two types of diagnostic tests discussed here are molecular lab-based PCR, which detects viral RNA, rapid PCR testing, and antigen-based testing, which detects viral proteins (the antigen). PCR and antigen testing are described more fully below to help make strategic decisions regarding community testing, planning, and implementation.
A comparison of the technologies
Technology
There are different types of technologies used to test for SARS-CoV-2:
PCR test
- Detects viral RNA
- SARS-CoV-2 RNA is extracted from the sample (throat swab, nasal swab, or saliva sample)
- PCR—a type of nucleic acid amplification test—is then used to detect the viral genome
PCR test
- Detects viral RNA
- SARS-CoV-2 RNA is extracted from the sample (throat swab, nasal swab, or saliva sample)
- PCR—a type of nucleic acid amplification test—is then used to detect the viral genome
Lab-based PCR
“Lab-based PCR” molecular diagnostic testing uses well-established lab processes that are run in a laboratory by trained technicians.
Rapid PCR
“Rapid PCR” tests use relatively new technology that simplifies the testing process by allowing it to be performed at the site of sample collection, or point of care (POC).
Antigen test
- Detects the antigen—in this case, viral proteins
- The saliva sample or nasal swab sample is added to a surface coated with antibodies that bind to specific viral proteins; this is used to create a signal that detects the virus
Antigen test
- Detects the antigen—in this case, viral proteins
- The saliva sample or nasal swab sample is added to a surface coated with antibodies that bind to specific viral proteins; this is used to create a signal that detects the virus
When to use
PCR test
- When you need accurate results with high confidence
- Ideal for diagnostic and population surveillance testing, especially in a high-volume setting
- If you have symptoms and a negative antigen test result, get a PCR test for confirmation.1 If you have symptoms or are asymptomatic and have a positive antigen test result, get a PCR test for confirmation.
PCR test
- When you need accurate results with high confidence
- Ideal for diagnostic and population surveillance testing, especially in a high-volume setting
- If you have symptoms and a negative antigen test result, get a PCR test for confirmation.1 If you have symptoms or are asymptomatic and have a positive antigen test result, get a PCR test for confirmation.
Lab-based PCR
Lab-based PCR tests are ideal for high-volume processing, supporting local and national-level testing such as in schools and corporations.
Rapid PCR
Rapid PCR POC tests are ideal for evaluating high-risk congregate settings such as emergency rooms, clinics, hospitals, and nursing homes.
Antigen test
- When you need convenience and speed to quickly determine if a person may have the virus
- Ideal for point-of-care testing and screening high-risk congregate settings—not for asymptomatic populations 2,3
Antigen test
- When prevalence is high and you need to quickly determine if a symptomatic person may have the virus
- For testing or screening of asymptomatic individuals in settings where serial testing is possible 2
Accuracy
 | Accuracy of a PCR test takes into account the sensitivity and specificity of how correctly the test can identify whether a sample is infected with SARS-CoV-2 viral RNA. Both lab-based and rapid PCR tests have high sensitivity and high specificity,* meaning that either test will correctly detect the presence of SARS-CoV-2 RNA in samples from patients who have COVID-19. Diagnostic PCR tests are considered the gold standard for viral detection and provide accurate results with high confidence. |
PCR test
- PCR tests have are considered the “gold standard” for detecting whether the virus is present
- Highly sensitive PCR tests can detect low viral loads, even in the absence of symptoms
PCR test
- PCR tests have very high sensitivity for detection of the virus and are considered the “gold standard” for detecting whether the virus is present.
- Highly sensitive PCR tests can detect low viral loads, even in the absence of symptoms
Antigen test
- In one study, an antigen test had a sensitivity of 64% in symptomatic cases, meaning 36% (~2 in 5) positive cases receive a negative result (known as false negatives)*
- In the same study, the antigen test had a sensitivity of 36% in asymptomatic cases, meaning 64% (~3 in 5) of positive cases receive a negative result (false negatives)*
Scalability
PCR test
- A PCR instrument is capable of running thousands of samples per day
PCR test
A PCR instrument is capable of running thousands of samples per day
Lab-based PCR
Most lab-based PCR tests can accommodate 96 to 384 samples (including controls) simultaneously on a single test plate, which is considered high throughput.
Rapid PCR
Most rapid PCR tests can process one sample at a time, which is considered low throughput. The number of patient samples that can be run simultaneously is determined by the availability of instruments and staff at the testing site.
Antigen test
- Requires significant hands-on time for trained operators to administer and interpret results.
- To run a large number of samples, many test kits and personnel are needed.
Antigen test
- Requires significant hands-on time for trained operators to administer and interpret results.
- To run a large number of samples, many test kits and personnel are needed.
Turnaround time
PCR test
- It can take as little as 24 hours to get results
PCR test
It can take as little as 24 hours to get results
Lab-based PCR
Lab-based PCR tests are ideal for high-volume processing, supporting localand national-level testing such as in schools and corporations.
Rapid PCR
Rapid PCR POC tests are ideal for evaluating high-risk congregate settings such as emergency rooms, clinics, hospitals, and nursing homes.
Antigen test
Antigen test
It can take up to 30 minutes to report out each individual result, especially if the result is negative
For the latest guidelines, please refer to:
The CDC:
https://www.cdc.gov/coronavirus/2019-ncov/lab/testing.html
https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html
The European CDC:
https://www.ecdc.europa.eu/en/publications-data/options-use-rapid-antigen-tests-covid-19-eueea-and-uk
The World Health Organization:
https://www.who.int/publications/i/item/antigen-detection-in-the-diagnosis-of-sars-cov-2infection-using-rapid-immunoassays
Testing technology and community needs
The decision to include PCR and antigen technologies in a testing program depends on the unique needs of the community. Importantly, community leaders should consider the organization's tolerance of an incorrect answer and the acceptability of that risk: what are the potential downstream effects of allowing an infected individual into the community because of a false negative result? Does convenience outweigh accuracy?
A clear understanding of the testing options is the first step in designing a testing program that will help keep the community safe. PCR tests, the gold standard for SARS-CoV-2 testing, provide high accuracy and therefore high confidence in the test results. Antigen tests are convenient when only a few results are needed, which may be advantageous in the point-of-care setting.
References
Style Sheet for Global Design System
Style Sheet for Komodo Tabs