Article

It’s hard to believe that it’s been more than 2 years since the World Health Organization (WHO) declared COVID-19 a global pandemic on March 11, 2020. At that time, the scientific world and public health communities all came together to identify the cause of this outbreak, to understand the type of “virus” infecting people and identify the infectious “disease” causing so many deaths around the world.

Fast forward to the first five months of 2022, where we now find ourselves removing COVID-19 restrictions at the same time cases are rising in the U.S. due to the “newest” Omicron subvariant BA.2.12 and BA2.12.1¹ wave.

How many SARs-CoV-2 variants of concern (VOC) are there?

What We Know about Omicron

It’s amazing how much we have learned about COVID-19 during these past two years of the pandemic. SARS-CoV-2, like other RNA viruses², is prone to genetic evolution while adapting to their new human hosts with the development of mutations over time, resulting in the emergence of multiple variants that may have different characteristics compared to its ancestral strains. Viruses mutate all the time, but only some mutations affect their ability to spread or evade prior immunity from vaccination or infection, or the severity of disease they cause.

The evolution of the SARS-CoV-2 virus over the course of the COVID-19 pandemic has resulted in the emergence of five variants of concern (VOC)³—Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1) Delta (B.1.617.2) and Omicron (B.1.1.529): —to date. In late December 2021, Omicron overtook Delta as the dominant variant in the U.S, and by the end of April 2022, surpassed the original Omicron strain to become the predominant COVID-19 variant in the U.S.

The Omicron variant, officially known as B.1.1.529, of SARS-CoV-2 has three main subvariants in its lineage⁴: BA.1, BA.2 and BA.3. Omicron has also undergone 50 mutations when compared to its previous variants of SARS-CoV-2: Alpha, Beta, Gamma, and Delta, and it is found to be the most prominent and distinct VOC as the spike protein of Omicron has 26 amino acid mutations from the millions of SARS-CoV-2 genomes.⁵

The BA.1 subvariant has over 30 mutations⁶ in the spike protein that helps it enter cells. Spike protein mutations⁷ are of high concern to scientists and public health officials because they affect how infectious a particular variant is and whether it is able to escape the protective antibodies that the body produces after vaccination or a prior COVID-19 infection.

BA.2 or the “stealth variant” has eight unique mutations that make it more transmissible than the original Omicron variant, but lacks the 13 mutations that BA.1 has. BA.2 does, however, share around 30 mutations with BA.1.⁸

XE: A hybrid variant of Omicron

The XE sub-variant is a recombinant hybrid strain of Omicron BA.1 and BA.2 that contains mutations found in both variants. A recombinant occurs when two or more variants of the virus infects the same cell, in the same person, at the same time, and combines their genetic material.⁹ Omicron XE appears to be more transmissible than Omicron BA.2, which appears to be more transmissible than Omicron BA.1.

Is Omicron more transmissible than previous variants?

According to the CDC, the Omicron variant spreads more easily than the original SARS-CoV-2 virus and the Delta variant. BA.2 shares many genetic similarities with its BA.1 subvariant, but BA.2 is between 30 percent and 50 percent more contagious than BA.1, appears to spread even faster that BA.1, but it does not appear to cause more severe disease than BA.1.¹⁰

A continued need for POC COVID-19 molecular testing

While the COVID-19 virus is still with us and continues to evolve, we should expect to see new variants emerge and disappear as they compete against each other and other circulating viruses. We should continue to protect ourselves and use the tools that we have at our disposal to respond to this ongoing pandemic.

COVID-19 testing is critical and remains important to help keep life moving forward, as new variants may continue to emerge.¹³ While there are many different types of tests that have emergency use authorization (EUA) in the United States, including molecular diagnostics/nucleic acid amplification tests (NAAT), antigen tests, and serological tests, molecular testing remains the gold standard for identifying SARS-CoV-2 infection.¹¹

“Current diagnostic tests for the SARS-CoV-2 pandemic use nucleic acid, antibody and protein-based detections, but viral nucleic acid detection by RT–PCR remains the gold standard.”

–Kevadiya, et al.¹²

Talis One™: The next big thing in COVID-19 molecular testing

At Talis, we believe that accurate POC molecular tests that can provide results in minutes instead of hours are needed to meet the need for fast, accurate testing. But not all POC NAATs deliver the same accuracy and sensitivity that central lab NAATs deliver¹², which is why we developed the Talis One COVID-19 Test System.

Designed to deliver central lab quality NAAT results quickly and in a variety of care environments, the Talis One COVID-19 Test System is the answer for rapid, POC COVID-19 molecular testing needs. Unlike other POC COVID-19 tests that may not be as sensitive, the Talis One COVID-19 Test System achieves lab-quality detection thanks to our proprietary on-cartridge sample extraction step and other patented technologies that give our assay a limit of detection (LOD) of 500 copies/mL.

COVID-19 Molecular Testing Resources

• CDC: Overview of Testing for SARS-CoV-2 (COVID-19)
• IDSA Guidelines on the Diagnosis of COVID-19: Molecular Diagnostic Testing

References

1. CDC Tracker Interpretive Summary for April 22, 2022. Unpacking Variants. J Phys Chem Lett Omicron BA.2 (B.1.1.529.2): High Potential for Becoming the Next Dominant Variant 2022 May 5;13(17):3840-3849. Epub 2022 Apr 25.
2. National Library of Medicine – Emerging Variants of SARS-CoV-2 And Novel Therapeutics Against Coronavirus (COVID-19) 2022 Feb 6. Aleem A, Akbar Samad AB, Slenker AK.
3. National Library of Medicine – Emerging Variants of SARS-CoV-2 And Novel Therapeutics Against Coronavirus (COVID-19) 2022 Feb 6. Aleem A, Akbar Samad AB, Slenker AK.
4. CDC-COVID-19 SARS-CoV-2 Variant Classifications and Definitions
5. Eur Phys J Plus. 2022; 137(1): 100. – Published online 2022 Jan 10 doi: 10.1140/epjp/s13360-021-02321-y.
6. Acta Pharmacologica Sinica- Review Article. Published: 03 August 2020. Structural and functional properties of SARS-CoV-2 spike protein: potential antivirus drug development for COVID-19. Huang, Y., Yang, C., Xu, Xf. et al.
7. Acta Pharmacologica Sinica volume 41, pages 1141–1149 (2020). Structural and functional properties of SARS-CoV-2 spike protein: potential antivirus drug development for COVID-19. Huang, Y., Yang, C., Xu, Xf. et al.
8. N Engl J Med 2022; 386:1579-1580. Neutralization of the SARS-CoV-2 Omicron BA.1 and BA.2 Variants.
9. UK SARS-CoV-2 variants of concern and variants under investigation in England. Technical briefing 40Security. What is Omicron XE Variant and is there cause for concern?
10. MedRxiv and BioRxiv. Occurrence and significance of Omicron BA.1 infection followed by BA.2 reinfection. Posted February 22, 2022.
11. The Infectious Diseases Society of America Guidelines on the Diagnosis of COVID-19: Molecular Diagnostic Testing. Published. 2021 Jan 22. doi:10.1093/cid/ciab048. Hanson KE, Caliendo AM, Arias CA, et al.
12. Diagnostics for SARS-CoV-2 infections. Nat Mater. Published 2021;20(5):593-605. doi:10.1038/s41563-020-00906-z. Kevadiya BD, Machhi J, Herskovitz J, et al.
13. COVID-19 Testing: What You Need to Know – Updated May 3, 2022.

Whether upcoming travel is for relaxation, business, or a combination of both, testing for COVID-19 is likely an integral part of the trip, especially when traveling by air. There are often very specific requirements on the type of test that will be accepted, and patients may be turning to their healthcare providers for advice. In this article, we provide links to relevant resources and a quick explanation of what qualifies as a nucleic acid amplification test (NAAT) COVID-19 test for travel purposes to help you provide your patients with effective advice.

A PCR test vs a NAAT COVID-19 test for travel—what’s the difference?

One question the Talis team frequently hears is if the Talis One™ COVID-19 Test System, which has been granted Emergency Use Authorization (EUA),^† can be used for travel testing. Patients have often heard the term “PCR” test when most of the time any NAAT will work. Consequently, many worry that if they don’t get a PCR test, the test won’t be valid as they are trying to board a domestic or an international flight.

The technology in the Talis One COVID-19 Test System is a specific NAAT that falls under the category of isothermal amplification techniques. You can learn more about our technology here, but briefly, our tests use real-time loop-mediated isothermal amplification (rtLAMP) for DNA targets and real-time reverse transcription loop-mediated isothermal amplification (rtRT-LAMP) for RNA targets. This approach is recognized as a NAAT technology that is used for SARS-CoV-2 testing by the CDC.¹

Additional resources on COVID-19 testing for travel that your patients may want

One of the biggest challenges with knowing which tests are valid is understanding the different jurisdictions and where to look for more information. Here are a few tips that your patients may find useful:

For international travel, look for information based on your destination.

Each country has their own rules about what is required for travel into the country, with a variety of mask mandates and acceptable tests which may vary based on vaccine status. For travel from the United States to other countries, the State Department has a page on their website where you can look up country-specific COVID-19 information.

For Air Travelers to the U.S.A.

For travel into the United States from a foreign country, all air passengers regardless of nationality or vaccination status, are required to show documentation of a negative Covid-19 viral test result taken within one day before travel, or documentation of having recovered from COVID-19 in the past 90 days, before they board their flight.

For Land Travel to the U.S.A.

Effective January 22, 2022, the Department of Homeland Security (DHC) requires non-U.S. individuals who are traveling for both essential and non-essential reasons and are seeking to enter the United States via land ports of entry (POE) and ferry terminals at the U.S-Mexico and U.S-Canada borders, to be fully vaccinated for COVID-19 and provide related proof of vaccination, as COVID-19 cases continue to rise nationwide. This restriction does not apply to U.S. citizens, Lawful Permanent Residents, or U.S. nationals. Learn more about land travel requirements from DHS.

For travel within the United States, also look for information based on your destination.

While at the time of writing this article, most states are fully open and do not require COVID-19 testing for the fully vaccinated, the emergence of variants and local surges can alter conditions rapidly. One place to look for information at the state level is at each state’s health department. You can find links to each states, cities, and county health departments on the CDC’s website.

Note that some counties and cities may have more stringent requirements than the state they are in, so be sure to check those public health departments as well.

The emergence of viral variants and local COVID-19 surges can alter conditions quickly, so we recommend regular review of the relevant websites before and during travel.

References

1. CDC. CDC – Nucleic acid amplification tests (NAATs). Centers for Disease Control and Prevention. Published February 11, 2020. Accessed November 6, 2021.

As the SARS-CoV-2 omicron variant (B.1.1.529) rapidly became the dominant strain in South Africa in late 2021, public health officials around the globe recognized that a new, highly transmissible form of the virus was likely emerging.^1,2 However, understanding the specifics of what was different about omicron remained to be seen. Beyond higher transmissibility, questions around disease severity, vaccine effectiveness, and the time course of the disease were yet to be uncovered.

Now, in just a few short months since omicron was initially identified, a clearer picture of the variant is coming into focus. And with that clearer picture of omicron’s complex biology, we have a better understanding of how our testing practices need to adjust. In this article, we’ll provide a quick summary of what we now know about omicron, how that affects testing strategies, and what we can learn to be prepared for future variants.

What we know about omicron so far

Omicron carries many mutations¹

Compared to the original SARS-CoV-2 alpha strain (B.1.1.7), the genome of the omicron variant carries over 60 different mutations.¹ More than half of omicron’s mutations are in the spike protein,¹ which mediates cell attachment and entry.³ Interestingly, as with all of the SARS-CoV-2 variants of concern, the omicron spike protein carries the D614G mutation that is associated with higher viral loads in the upper respiratory tract and a younger patient age range.¹ Other mutations in the spike protein are associated with functionality that is expected to enhance infectivity.¹

Omicron is likely capable of at least partial immune evasion^4–6

Evidence reported in preprints suggests that omicron can evade immunity from previous infections^4–6 and vaccinations,⁵ leading to reinfection, as well as infection of vaccinated individuals. However, one of the studies is reporting that prior infection and vaccination do protect against hospitalization and death.⁶

Omicron is likely to cause less severe disease⁷

An analysis of COVID-19 patients in Southern California, including 52,297 cases infected with the omicron variant and 16,982 cases with the delta variant, suggests that omicron causes less severe disease than delta, even when you take into account vaccination status or previous SARS-CoV-2 infection.⁷ The caveat to this study is that it is still in the preprint stage and has yet to be peer-reviewed.

Omicron likely reproduces faster^8,9 and may have a shorter incubation period^10,11

Faster reproducibility is one of the critical features of omicron that may help explain its ability to out-compete other variants, such as delta, to become the dominant strain in a region.^8,9 Two studies still in the preprint stage report that the mean serial interval for omicron is 2.2 days⁸ and between 1.5 and 3.2 days.⁹ In contrast, reports of the mean generation time for delta spans a range of 3.3 – 4.24.^8,12,13

Early indications suggest that omicron also has a shorter incubation period than other variants. One early study in Denmark found a median incubation period of 3 days for omicron¹⁰, compared with 4.3 and 5.0 days for delta and other variants¹¹, respectively.

What this means for testing

Given omicron’s large mutational burden¹ and the early indications that it can evade prior immunity,^4–6 likely reproduces faster,^8,9 and may have shorter incubation times,^10,11 some public health agencies and healthcare systems are already rethinking their testing strategies.^14,15

Can PCR and antigen tests sensitively and accurately detect omicron?

The first thing to consider about testing is whether the large mutational burden carried by omicron affects the sensitivity and accuracy of either nucleic acid amplification tests (NAATs) like PCR or rapid antigen tests that rely on lateral flow technology.

A January 22, 2022, technical brief from the World Health Organization (WHO) observes that the diagnostic accuracy of the PCR and rapid antigen tests listed in their emergency use list (EUL) is not significantly affected by the omicron variant,¹⁵ although one of the deletions in the gene encoding the spike protein, the S gene ?69-70, can cause S gene target failure (SGTF) in some NAATs.

In addition, the Infectious Diseases Society of America (IDSA) is reporting that preliminary evidence suggests no loss in accuracy of currently available NAATs¹⁶ and that antigen tests are mostly based on detecting the nucleocapsid protein and should therefore be unaffected by the mutations in omicron.¹⁶

Both the GenBody COVID-19 Ag Test and the Talis One™? COVID-19 Test System are expected to accurately detect the new coronavirus variant omicron based on initial in silico studies.*

Does omicron affect testing frequency?

While the CDC has not made any updates to their testing recommendations in response to omicron,^17,18 the shorter generation and incubation times are leading some physicians to recommend frequent serial testing with rapid tests.¹⁹

What can we learn from omicron?

Emerging just as much of the world was beginning to relax COVID-19 protection measures, the omicron variant drove huge surges in infection rates, especially in the United States.²⁰ The good news is that, as the CDC notes, “we have the tools to fight omicron”.¹⁸ Vaccines, masks, and testing are all effective tools that remain highly effective against omicron.¹⁸ What’s critical is that we keep on the lookout for the emergence of new variants and adjust our practices as quickly as we can based on initial and evolving evidence.

Talis is proud of our part in delivering pandemic-mitigating solutions, with the GenBody COVID-19 Ag Test and the Talis One COVID-19 Test System.

References

1. He X, Hong W, Pan X, Lu G, Wei X. SARS-CoV-2 Omicron variant: Characteristics and prevention. MedComm. 2021;2(4):838-845. doi:10.1002/mco2.110
2. Viana R, Moyo S, Amoako DG, et al. Rapid epidemic expansion of the SARS-CoV-2 Omicron variant in southern Africa. Nature. Published online January 7, 2022:1-10. doi:10.1038/s41586-022-04411-y
3. Shang J, Wan Y, Luo C, et al. Cell entry mechanisms of SARS-CoV-2. Proc Natl Acad Sci. 2020;117(21):11727-11734. doi:10.1073/pnas.2003138117
4. Altarawneh H, Chemaitelly H, Tang P, et al. Protection afforded by prior infection against SARS-CoV-2 reinfection with the Omicron variant. medRxiv. Published online January 1, 2022:2022.01.05.22268782. doi:10.1101/2022.01.05.22268782
5. Yang W, Shaman J. SARS-CoV-2 transmission dynamics in South Africa and epidemiological characteristics of the Omicron variant. medRxiv. Published online January 1, 2021:2021.12.19.21268073. doi:10.1101/2021.12.19.21268073
6. Pulliam JRC, van Schalkwyk C, Govender N, et al. Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa. medRxiv. Published online January 1, 2021:2021.11.11.21266068. doi:10.1101/2021.11.11.21266068
7. Lewnard JA, Hong VX, Patel MM, Kahn R, Lipsitch M, Tartof SY. Clinical outcomes among patients infected with Omicron (B.1.1.529) SARS-CoV-2 variant in southern California. medRxiv. Published online January 1, 2022:2022.01.11.22269045. doi:10.1101/2022.01.11.22269045
8. Kim D, Jo J, Lim JS, Ryu S. Serial interval and basic reproduction number of SARS-CoV-2 Omicron variant in South Korea. medRxiv. Published online January 1, 2021:2021.12.25.21268301. doi:10.1101/2021.12.25.21268301
9. Abbott S, Sherratt K, Gerstung M, Funk S. Estimation of the test to test distribution as a proxy for generation interval distribution for the Omicron variant in England. medRxiv. Published online January 1, 2022:2022.01.08.22268920. doi:10.1101/2022.01.08.22268920
10. Brandal LT, MacDonald E, Veneti L, et al. Outbreak caused by the SARS-CoV-2 Omicron variant in Norway, November to December 2021. Eurosurveillance. 2021;26(50):2101147. doi:10.2807/1560-7917.ES.2021.26.50.2101147
11. Grant R, Charmet T, Schaeffer L, et al. Impact of SARS-CoV-2 Delta variant on incubation, transmission settings and vaccine effectiveness: Results from a nationwide case-control study in France. Lancet Reg Health – Eur. 2021;0(0). doi:10.1016/j.lanepe.2021.100278
12. Hwang H, Lim JS, Song SA, et al. Transmission Dynamics of the Delta Variant of SARS-CoV-2 Infections in South Korea. J Infect Dis. Published online December 2, 2021:jiab586. doi:10.1093/infdis/jiab586
13. Li L, Han ZG, Qin PZ, et al. Transmission and containment of the SARS-CoV-2 Delta variant of concern in Guangzhou, China: A population-based study. PLoS Negl Trop Dis. 2022;16(1):e0010048. doi:10.1371/journal.pntd.0010048
14. Omicron Guidance Updates | Nebraska Medicine Omaha, NE. Accessed January 26, 2022.
15. Enhancing response to Omicron SARS-CoV-2 variant. Accessed January 26, 2022.
16. Vaccines FAQ. Accessed January 26, 2022.
17. CDC. Healthcare Workers. Centers for Disease Control and Prevention. Published February 11, 2020. Accessed January 26, 2022.
18. CDC. Omicron Variant: What You Need to Know. Centers for Disease Control and Prevention. Published December 20, 2021. Accessed January 27, 2022.
19. Godoy M. Why rapid COVID tests aren’t more accurate and how scientists hope to improve them. NPR. Published January 23, 2022. Accessed January 26, 2022.
20. CDC. COVID Data Tracker. Centers for Disease Control and Prevention. Published March 28, 2020. Accessed September 24, 2021.

*Internal test data on file and available upon request.

While the COVID-19 pandemic has brought phrases like “PCR test” and “antigen test” into wider use, one term that hasn’t been talked about as much is “NAAT,” which is short for nucleic acid amplification test (Figure 1).¹ As the media has widely reported,^2–7 most rapid COVID tests are antigen-based. Antigen tests are better at assessing if a person is infectious at the time of the testing rather than if they are carrying the SARS-CoV-2 virus, while lab-based PCR tests are better able to detect if a person has the virus.^2,3,5–7

If you’re a healthcare professional or facility manager looking for a point-of-care testing system that can help support a COVID-free environment, you may be wondering where NAATs fit into all of this. There are some rapid tests that are not antigen tests and not PCR tests, but rather are described as NAATs. We’ve already covered the difference between antigen and molecular tests in another blog post . In this article, we’ll discuss the differences between NAAT and PCR, focusing on point-of-care testing for COVID-19 and other infectious diseases.

PCR is a type of NAAT⁸

The quick answer to “what is the difference between NAAT and PCR” is that PCR is a type of NAAT. Not every NAAT uses PCR methodology, but all PCR tests are a type of NAAT.⁸

The term “NAAT” applies to a range of different technologies where nucleic acid, i.e., RNA or DNA, from a pathogen is amplified and detected to determine if a pathogen is present.⁸ Typically, if the pathogen is a virus with an RNA genome like SARS-CoV-2 and influenza, the first step in the NAAT method will be to convert the RNA into DNA using a reverse transcriptase and then amplify the DNA.

Different NAATs approach nucleic acid amplification in different ways.⁸

PCR

The lab-based COVID-19 test that is considered the gold-standard uses real-time reverse transcriptase PCR (RT-PCR), which converts SARS-CoV-2 RNA into DNA and then amplifies the DNA by cycling it through different temperatures.⁹ By including a high temperature step in each cycle, the two DNA strands are separated, and each strand replicated, enabling the generation of many copies of the same DNA sequence from a single molecule.¹⁰

When PCR is used in lab tests, the process can take hours because of the need to extract the nucleic acid from the specimen¹¹ and because the sample is typically run through thirty or more cycles of several minutes each (for a description of the COVID-19 testing process that is accessible to a general reader, see this article from NPR¹²).

Isothermal methods

Because PCR is a complex process that can take hours to perform,¹¹ it is less suitable for a point-of-care test where results are needed in thirty minutes or less. To address this challenge, several diagnostics developers have focused on nucleic acid amplification methods that do not require multi-temperature cycles, such as RT-LAMP technology. This collection of techniques is referred to as “isothermal” because amplification is conducted at a single temperature.^{13, 14} Amplification can be achieved in minutes, instead of hours, using different enzymatic techniques to separate the two DNA strands prior to replication.^{13, 14}

Not every NAAT delivers the same performance, especially point-of-care NAATs

From a practical point-of-view, you may be wondering if NAATs, especially point-of-care NAATs, can deliver the same quality results as lab-based PCR tests? When it comes to COVID-19, not every NAAT does,¹⁵ although more studies in real-world conditions are needed to confidently address this question.¹⁵

The Talis One COVID-19 Test System includes a nucleic acid extraction step to achieve central lab-level performance

One possible reason that some point-of-care NAATs don’t perform as well as lab-based PCR tests is that they don’t include a nucleic acid extraction step.¹¹ While this saves time, compounds in the sample can potentially inhibit the amplification step.¹¹ This is why the Talis team developed an instrument, the Talis One, that performs a solid-phase sample extraction step within the Talis One test cartridge; this enables the test system to achieve central lab-level performance.¹⁶

The difference between NAAT and PCR: non-PCR NAAT’s hold great promise for fast and accurate testing at the point of care

Bringing the sensitivity and specificity of PCR to the point of care requires looking beyond PCR to isothermal NAAT methods.^{13, 14} Whether these tests are used for the ongoing COVID-19 pandemic or for other infectious diseases, non-PCR NAAT’s hold great promise for ensuring fast and accurate test results in a variety of care settings.^{13, 14}

References

1. Google Trends. Google Trends. Accessed November 6, 2021.
2. How Accurate Are At-Home COVID Tests? Here’s What Experts Say. NBC Chicago. Accessed November 6, 2021.
3. Rapid COVID-19 Tests: When to Use Them and How They Work. Healthline. Published October 13, 2021. Accessed November 6, 2021.
4. Parker-Pope T. How to Use Rapid Home Tests (Once You Find Them). The New York Times. Published October 8, 2021. Accessed November 6, 2021.
5. The differences to know between COVID tests as gatherings begin for the holidays. Masslive. Published November 5, 2021. Accessed November 6, 2021.
6. Santora T. The Smartest Way to Use Rapid At-Home COVID Tests. Scientific American. Accessed November 6, 2021.
7. Hartmann M. Where Are All the At-Home COVID Tests? Intelligencer. Published October 27, 2021. Accessed November 6, 2021.
8. CDC – Nucleic acid amplification tests (NAATs). Centers for Disease Control and Prevention. Published February 11, 2020. Accessed November 6, 2021.
9. How is the COVID-19 Virus Detected using Real Time RT-PCR? Published March 27, 2020. Accessed November 18, 2021.
10. Polymerase Chain Reaction (PCR) Fact Sheet. Genome.gov. Accessed November 6, 2021.
11. Walker FM, Hsieh K. Advances in Directly Amplifying Nucleic Acids from Complex Samples. Biosensors. 2019;9(4):117. doi:10.3390/bios9040117
12. Appleby J. Why It Takes So Long To Get Most COVID-19 Test Results. NPR.  Published March 28, 2020. Accessed November 6, 2021.
13. Pumford EA, Lu J, Spaczai I, et al. Developments in integrating nucleic acid isothermal amplification and detection systems for point-of-care diagnostics. Biosens Bioelectron. 2020;170:112674. doi:10.1016/j.bios.2020.112674
14. James AS, Alwneh JI. COVID-19 Infection Diagnosis: Potential Impact of Isothermal Amplification Technology to Reduce Community Transmission of SARS-CoV-2. Diagnostics. 2020;10(6):399. doi:10.3390/diagnostics10060399
15. Dinnes J, Deeks JJ, Berhane S, et al. Rapid, point?of?care antigen and molecular-based tests for diagnosis of SARS?CoV?2 infection. Cochrane Database Syst Rev. 2021;2021(3):CD013705. doi:10.1002/14651858.CD013705.pub2
16. Talis Bio. Evaluation of the Talis One^TM Covid-19 Test System for the Rapid Detection of Sars-Cov-2 and Emerging Variants. Published online 2021. Accessed October 29, 2021.

The emergence of the SARS-CoV-2 Delta variant highlights the importance of widespread vaccination and the ongoing need for accurate testing.

New variants can quickly change the public health situation

Positive developments related to the pandemic situation between the end of 2020 and early 2021 generated a great deal of hope. Multiple vaccines were starting to become available and by March 8, 2021, the CDC declared that fully vaccinated people could gather indoors without wearing masks.¹ At that time, many believed that the worst of the pandemic was in the past. However, the emergence of the SARS-CoV-2 Delta variant significantly impacted the public health situation across much of the United States, with the CDC issuing new masking guidance and urging more people to become vaccinated in a July 27, 2021, announcement.²

As we now know, the Delta variant is ~2x more contagious than previous variants,^2-5 which has led to very rapid spread in areas with low vaccination rates.⁵ In the United States, the 7-day moving average of reported cases increased from ~12,000 in late June to ~60,000 by July 27.² One of the main lessons the medical community can learn from the rapid spread of the Delta variant is how quickly a new variant can change the local public health situation from in to out of control. So how can we stop the emergence of new variants, one or more of which may be worse than Delta?

Stopping the emergence of new variants requires controlling disease spread

As with many viruses, the emergence of SARS-CoV-2 variants is the result of random errors introduced into the viral genome during replication.⁶ The best way to reduce the emergence of new variants is to limit virus replication by limiting transmission.⁷

Variants are expected. The best way to slow the emergence of new variants is to reduce the spread of infection by taking measures to protect yourself, including getting a COVID-19 vaccine when available.⁷

Until vaccination rates increase sufficiently to limit transmission, SARS-CoV-2 testing will continue to be needed

Despite the effectiveness of vaccines in reducing the risk of death from SARS-CoV-2 and limiting disease spread, vaccine hesitancy remains a challenge.^8,9 Given a vaccination level of ~55% of the total population in the United States,¹⁰ it seems plausible that we may see additional outbreaks from new variants, although Delta is the only variant of concern currently in the United States.¹¹

In addition, many scientists believe that COVID-19 is here to stay, becoming an endemic disease.^12,13 Whether COVID-19, during its transition to endemicity, becomes a milder disease and/or a disease of the young,^12,13 diagnostic testing will most likely continue to be an important tool for ensuring public health.

References

1. CDC. CDC Museum COVID-19 Timeline. Centers for Disease Control and Prevention. Published August 4, 2021. Accessed August 23, 2021. https://www.cdc.gov/museum/timeline/covid19.html
2. CDC. Coronavirus Disease 2019 (COVID-19). Delta Variant: What We Know About the Science. Centers for Disease Control and Prevention. Published February 11, 2020. Accessed September 24, 2021. https://www.cdc.gov/coronavirus/2019-ncov/variants/delta-variant.html
3. Li B, Deng A, Li K, et al. Viral Infection and Transmission in a Large, Well-Traced Outbreak Caused by the SARS-CoV-2 Delta Variant.; 2021:2021.07.07.21260122. doi:10.1101/2021.07.07.21260122
4. Wang Y, Chen R, Hu F, et al. Transmission, viral kinetics and clinical characteristics of the emergent SARS-CoV-2 Delta VOC in Guangzhou, China. EClinicalMedicine. 2021;40:101129. doi:10.1016/j.eclinm.2021.101129
5. Bian L, Gao Q, Gao F, et al. Impact of the Delta variant on vaccine efficacy and response strategies. Expert Rev Vaccines.:1-9. doi:10.1080/14760584.2021.1976153
6. Chen J, Wang R, Wei G-W. Review of the mechanisms of SARS-CoV-2 evolution and transmission. ArXiv. Published online September 15, 2021:arXiv:2109.08148v1.
7. CDC. Coronavirus Disease 2019 (COVID-19). What you need to know about variants. Centers for Disease Control and Prevention. Published February 11, 2020. Accessed September 24, 2021. https://www.cdc.gov/coronavirus/2019-ncov/variants/variant.html
8. Tram KH, Saeed S, Bradley C, et al. Deliberation, Dissent, and Distrust: Understanding Distinct Drivers of Coronavirus Disease 2019 Vaccine Hesitancy in the United States. Clin Infect Dis Off Publ Infect Dis Soc Am. Published online July 16, 2021:ciab633. doi:10.1093/cid/ciab633
9. Siegler AJ, Luisi N, Hall EW, et al. Trajectory of COVID-19 Vaccine Hesitancy Over Time and Association of Initial Vaccine Hesitancy With Subsequent Vaccination. JAMA Netw Open. 2021;4(9):e2126882. doi:10.1001/jamanetworkopen.2021.26882
10. CDC. COVID Data Tracker. Centers for Disease Control and Prevention. Published March 28, 2020. Accessed September 24, 2021. https://covid.cdc.gov/covid-data-tracker
11. CDC. Coronavirus Disease 2019 (COVID-19). SARS-CoV-2 Variant Classifications and Definitions. Centers for Disease Control and Prevention. Published February 11, 2020. Accessed September 24, 2021. https://www.cdc.gov/coronavirus/2019-ncov/variants/variant-info.html
12. Torjesen I. Covid-19 will become endemic but with decreased potency over time, scientists believe. BMJ. 2021;372:n494. doi:10.1136/bmj.n494
13. Phillips N. The coronavirus is here to stay — here’s what that means. Nature. 2021;590(7846):382-384. doi:10.1038/d41586-021-00396-2

Healthcare disparities in the US have become strikingly apparent throughout the COVID-19 pandemic, affecting historically underserved populations (e.g., lower-income households, Black and Minority Americans, immigrants, people with disabilities, rural populations, etc.). Point-of-care (POC) testing can help. To reduce the spread of infections and bring health equity forward, we need to take a closer look at POC testing and how to get it to communities that need it most.

Healthcare disparities in the US at the point of care

The rapidity of spread and mortality associated with the COVID-19 pandemic has shined a light on health disparities in the US. COVID-19 infection is higher among groups already affected by health disparities across age, race, ethnicity, language, income, and living conditions.¹ Since the beginning of the pandemic, the top-third of vulnerable counties (defined by the COVID-19 vulnerability Index) have seen 21% more cases and 47% more deaths than the bottom-third of vulnerable counties, despite receiving 27% fewer tests.^{2 3}

One study found that transportation barriers are associated with significantly higher odds of a positive COVID-19 test, which suggests a greater risk of disease exposure associated with reliance on public transit and/or shared rides, or it may suggest inadequate access to health care, including timely COVID-19 testing.¹ What’s more, COVID-19 has shifted the utilization of the American healthcare system where individuals are delaying or forgoing care—which can have serious and life-threatening health consequences. By June 2020, over 40% of U.S. adults reported that they delayed health care due to COVID-19 concerns.⁴

Adding to these challenges is the threat of false negative COVID-19 test results, which could potentially lead to positive case clusters.^{5 6} When false negatives are suspected, individuals have to leave the facility and wait for their reflex testing results to become available. Ideally, individuals awaiting reflex testing results (as well as those who receive a positive COVID-19 test result) will quarantine, but this is not always possible, especially for those relying on public transportation and living in overcrowded housing facilities.

Minimizing the time it takes to get accurate results and being able to communicate those results to patients quickly is paramount for minimizing community spread and delivering proper treatment. This supports the need for rapid and reliable testing, as well as in-visit test-to-answer POC workflows—especially for communities that have been shown to have less access to medical care and are less inclined to use telehealth service.

What Point-of-Care Diagnostic Tests Should Look Like

To drive health equity forward, we need diagnostic testing to be more accessible and reliable for underserved populations.

Point-of-care diagnostics should enable rapid and effective test-to-treat workflows all in one visit

Because underserved populations are more likely to miss appointments due to transportation and are more likely to have limited access to telehealth,^7-10 it is imperative that these individuals get the information and treatment they need while they are in the testing facility. To confidently make treatment decisions during the same visit, point of care diagnostic tests should be sensitive without compromising speed and operational efficiency.

Not only will test-to-treat workflows at the point of care help detect disease and deliver proper care earlier, but it can help minimize health care expenses due to missed appointments and hospitalization. This approach is stressed in the Sexually Transmitted Infections National Strategic Plan (2021-2025), where several objectives are discussed to ensure continuity of care. The plan touches on expanding personnel training to enhance screening, testing, and treatment capabilities within a single facility, specialized programs, and integrated and collaborative approaches in settings that serve communities disproportionately affected by STIs, HIV, and viral hepatitis.¹¹

Point-of-care diagnostics should be flexible enough to adapt to different environments and different communities

Point-of-care locations can range from large pop-up centers in rural areas and places of work to metropolitan mobile clinics. Each community is unique, and POC tests need to be adaptable to the specific needs of the community. The instruments being used to detect SARS-CoV-2 should be space efficient for multiple types of facilities and, ideally, flexible enough to test for multiple infectious diseases and disease variants that are prevalent in the community being tested. This can save time for both the individual and the testing facility.

As suggested by the Office of the Assistant Secretary of Health (OASH) and Office of Minority Health (OMH), to expand access to communities that are unable to access traditional testing sites, the federal government should partner with test kit manufacturers to develop SARS-CoV-2 test kits that are flexible enough to be used at the point of care or at-home and should establish and enforce policies that require public and private health insurance to cover SARS-CoV-2 testing to minimize financial barriers.¹²

Point-of-care diagnostics should be easy-to-implement and easy-to-use

Adopting new healthcare technologies is resource intensive—requiring a substantial amount of time for implementation and training. With healthcare personnel shortages increasing in underserved areas,¹³ it can be difficult to maintain an efficient operational workflow, or worse, patients cannot get the tests they need because there aren’t enough people to perform them. POC testing needs to be easy to implement and intuitive so that facilities can get up and running as quickly as possible and maintain efficiency through personnel changes.

Point-of-care diagnostics should have features that streamline reporting and communication to patients, labs and governing bodies

Timely reporting is essential for sharing results, monitoring where outbreaks occur, tracking the incidence and prevalence of infection, and evaluating the impact of interventions. Not only can it help determine if a newly placed mobile clinic is effective and quickly get test results to patients, but it also enables proper allocation of critical resources to those in greatest need.

Moving Towards Health Equity with Point-of-Care Testing

With the CDC planning to invest $2.25 Billion to address COVID-19-related health disparities and advance health equity among populations that are at high-risk and underserved,¹⁴ there is no better time than now to evaluate and adopt a new POC testing solution.

To ensure there is timely and equitable access to testing with rapid return of results in communities disproportionately affected by COVID-19, we need to consider the recommendations outlined by the CDC:^{1 5}

• Use a social vulnerability index¹⁶ to help select testing sites
• Review the groups to prioritize for screening testing
• Carefully consider the different types of SARS-CoV-2 tests when planning for diagnostic or screening use

By providing easy access to actionable results at the point-of-care in public health settings, the Talis One molecular testing solution empowers you to quickly and confidently diagnose infections, promote safety and peace of mind for your patients, and ultimately combat healthcare disparities in the US.

References

1. Rozenfeld, Yelena, et al. “A model of disparities: risk factors associated with COVID-19 infection.” International journal for equity in health 19.1 (2020): 1-10.
2. Bringing Greater Precision to the COVID-19 Response. (2020, December). Retrieved July 01, 2021, from https://precisionforcovid.org/ccvi
3. Smittenaar, P., Stewart, N., Sutermaster, S., Coome, L., Dibner-Dunlap, A., Jain, M., … & Sgaier, S. K. (2021). A COVID-19 Community Vulnerability Index to drive precision policy in the US. medRxiv.
4. Czeisler, Mark É., et al. “Delay or avoidance of medical care because of COVID-19–related concerns—United States, June 2020.” Morbidity and mortality weekly report 69.36 (2020): 1250.
5. False negative rate of COVID-19 PCR testing: A discordant testing analysis. (2021, January 9). Retrieved July 01, 2021, from https://virologyj.biomedcentral.com/articles/10.1186/s12985-021-01489-0
6. Cao G, Tang S, Yang D, Shi W, Wang X, Wang H, et al. The potential transmission of SARS-CoV-2 from patients with negative RT-PCR swab tests to others: two related clusters of COVID-19 outbreak. Jpn J Infect Dis. 2020. https://doi.org/10.7883/yoken.JJID.2020.165.
7. Samuels, R. C., Ward, V. L., Melvin, P., Macht-Greenberg, M., Wenren, L. M., Yi, J., … & Cox, J. E. (2015). Missed appointments: factors contributing to high no-show rates in an urban pediatrics primary care clinic. Clinical pediatrics, 54(10), 976-982.
8. Fischer, S. H., Ray, K. N., Mehrotra, A., Bloom, E. L., & Uscher-Pines, L. (2020). Prevalence and characteristics of Telehealth utilization in the United States. JAMA network open, 3(10), e2022302-e2022302.
9. Pierce, R. P., & Stevermer, J. J. (2020). Disparities in use of telehealth at the onset of the COVID-19 public health emergency. Journal of telemedicine and telecare, 1357633X20963893.
10. Vogels, E. (2021, June 22). Digital divide persists even as Americans with lower incomes make gains in tech adoption. Retrieved July 01, 2021, from https://www.pewresearch.org/fact-tank/2021/06/22/digital-divide-persists-even-as-americans-with-lower-incomes-make-gains-in-tech-adoption/
11. U.S. Department of Health and Human Services. 2020. Sexually Transmitted Infections National Strategic Plan for the United States: 2021–2025. Washington, DC.
12. COVID-19 Health Equity Task Force: Long COVID, PPE, Testing and Therapeutics Subcommittee Interim Recommendations. (2021, June 25). Retrieved July 01, 2021, from https://www.minorityhealth.hhs.gov/Assets/PDF/June-COVID19HETFSubcommitteesRecommendations-062521-508.pdf
13. Malayala, Srikrishna Varun, et al. “Primary care shortage in medically underserved and health provider shortage areas: Lessons from Delaware, USA.” Journal of Primary Care & Community Health 12 (2021): 2150132721994018.
14. CDC announces $2.25 billion to address Covid-19 health disparities in communities that are at high-risk and underserved. (2021, March 17). Retrieved July 01, 2021, from https://www.cdc.gov/media/releases/2021/p0317-COVID-19-Health-Disparities.html
15. Overview of Testing for SARS-CoV-2 (COVID-19). (2021, March 17). Retrieved July 01, 2021, from https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html
16. CDC/ATSDR Social Vulnerability Index. (2021, April 28). Retrieved July 01, 2021, from https://www.atsdr.cdc.gov/placeandhealth/svi/index.html

In the antigen vs molecular test debate, understanding which test is best is a matter of timing and application—the answer could change depending on how you’re using the test and how quickly you need the test results. In addition, the emergence of newer testing technologies may change the parameters of the debate, tipping the balance towards molecular testing for a number of situations.

To understand which test technology will work best for your application, let’s take a closer look at the pros and cons of each technology (note that for the sake of brevity, we are leaving the discussion of sample type for another article).

Molecular tests performed in a central lab are sensitive and specific, but take time to deliver results

What a molecular test detects

In general, molecular tests detect nucleic acid—either RNA or DNA.

Why this matters for diagnosing COVID-19

Molecular tests can detect the presence of SARS-CoV-2 even during the early stages of infection because they detect viral RNA, which can accumulate to high levels within a cell before virus particles are formed.

Benefits of molecular tests

Molecular tests are ideal for detecting emerging infectious diseases such as the SARS-CoV-2 virus because they are quick to develop and deploy.

Most molecular tests that are conducted in a central lab setting are very sensitive and specific, with commercially available SARS-CoV-2 molecular tests exhibiting >95% sensitivity and >99% specificity, with the potential to detect as little as a few dozen to a few hundred copies/mL of a nucleic acid sequence from the pathogen (i.e., they have low limits of detection (LOD)).¹

Thus, molecular tests can detect disease in the very early stages of infection, when the viral load is fairly low.

Challenges of molecular tests

While the sensitivity and specificity of lab-conducted molecular tests is high and the LOD is low, the complexity of these tests typically restricts their use to the central lab setting. This adds time between when the sample is taken and when results are delivered. At best, the turnaround time can be as little as 24-48 hours, but at the height of the pandemic, some labs were experiencing turnaround times of as much as two weeks due to reagent shortages and insufficient testing throughput.

For highly infectious diseases like SARS-CoV-2, the delay in receiving test results can negatively impact both the patient—by potentially forcing them to quarantine while waiting for results—and public health, if an infectious patient does not quarantine while waiting for results.

Best applications for SARS-CoV-2 molecular tests

With their high sensitivity and specificity, SARS-CoV-2 molecular tests are often considered the gold standard for diagnosis. The Infectious Disease Society of America (ISDA) recommends molecular tests for symptomatic patients even if the suspicion of COVID-19 is low, and prefers that results be available within 48 hours.²

For asymptomatic patients, the ISDA recommends testing only in certain situations², such as:

• Upon known or suspected exposure to COVID-19
• Upon admission to a hospital in an area with a high prevalence of COVID-19
• Before certain medical procedures

Antigen tests can be performed at the point-of-care, but are not as sensitive as molecular tests leading to higher false negative rates

What an antigen test detects

In general, an antigen test detects a protein that’s unique to the pathogen. For SARS-CoV-2 detection, the antigen tests detect a protein of the virus particle.

Why this matters for diagnosing COVID-19

Because antigen tests rely on production of virus particles, they can miss newly-infected patients that have virus replicating within their cells but have not yet produced measurable amounts of virus particles.

Benefits of antigen tests

Antigen tests are easy to conduct, inexpensive, and deliver results in minutes. They are also highly specific and can be done at the point-of-care.³

Challenges of antigen tests

The benefits of antigen testing are balanced by a lower sensitivity than molecular tests, with sensitivity dependent on whether or not symptoms are present and how long after symptom onset the test is given. For tests given within seven days of symptom onset, pooled antigen test sensitivity is 84%, dropping to 49% in asymptomatic individuals.³

The lower sensitivity can lead to a higher false negative rate, i.e., more missed infections, which restricts their usefulness to certain situations when molecular tests are widely available.

Best applications for SARS-CoV-2 antigen tests

While the ISDA recommends molecular tests over antigen tests for symptomatic individuals unless test results will not be delivered within three days, their recommendations for asymptomatic individuals are neither for nor against antigen testing due to a lack of sufficient evidence either way.³

That said, a more recent simulation study based on real-world data suggests that although RT-PCR tests perform better than antigen tests in detecting infected individuals and preventing transmission, more frequent antigen testing, e.g., every day or every 3 days, is comparable to less frequent RT-PCR tests, at the expense of many more false-negative tests. This indicates that frequent antigen tests, potentially self-administered at home could be an important tool in combating spread of infection.⁴

The Talis One delivers all the benefits of molecular tests with similar speed and convenience of antigen tests

As can be seen from the above discussion, the antigen vs. molecular test debate has primarily been one of test quality versus speed, with the molecular test being used as the gold standard, although it can take days to get results, and the antigen test being used when speed is more important than sensitivity.

However, the Talis One is set to change the cost/benefit balance in this debate. It’s a molecular test that can be done quickly and easily at the point-of-care, delivering results in under 30 minutes. And unlike other point-of-care tests, the Talis One’s unique cartridge technology includes solid-phase nucleic acid extraction, which gives it a sensitivity and LOD that’s comparable to molecular tests performed in a lab, enabling excellence at the point of care.

Conclusion

In the antigen vs. molecular test debate, the best test is the one that gives you the highest sensitivity and specificity in the shortest amount of time. Molecular testing is the gold standard, although antigen testing can be effective when speed is necessary. Now, with the Talis One, you can get similar speed and point-of-care convenience as an antigen test with the quality you could previously only get from a central lab molecular test.

References

1. Antigen and Molecular Tests for COVID-19. COVID-19 Testing Toolkit website. Accessed July 9, 2021. https://www.centerforhealthsecurity.org/covid-19TestingToolkit/molecular-based-tests/current-molecular-and-antigen-tests.html#Current-Molecular-Tests
2. Hanson KE, et al. IDSA Guidelines on the Diagnosis of COVID-19: Molecular Diagnostic Testing. Clin Infect Dis. 2020 Jun 16;ciaa760. doi: 10.1093/cid/ciaa760.
3. Hanson KE, et al. IDSA Guidelines on the Diagnosis of COVID-19: Antigen Testing. Clin Infect Dis. 2021 Jun 23;ciab557. doi: 10.1093/cid/ciab557.
4. Ke R, et al. In vivo kinetics of SARS-CoV-2 infection and its relationship with a person’s infectiousness. medRxiv. Preprint. 2021 Jun 30. doi: 10.1101/2021.06.26.21259581. Accessed July 10, 2021.

As new variants of SARS-CoV-2 arise, they can impact diagnostic testing, potentially resulting in false negative results. To confidently make treatment decisions, achieve best-possible patient outcomes, and drive operational and clinical efficiency in a point-of-care setting, you need highly sensitive, rapid molecular tests capable of detecting all existing and emerging SARS-CoV-2 variants.

Which SARS-CoV-2 Tests Are Susceptible to False Negatives?

Molecular tests are straightforward to design for pathogen detection because they are largely based on an RNA sequence. However, viruses that rapidly evolve, such as SARS-CoV-2, can influence test sensitivity based on the sequence of the variant, the design of the test and the prevalence of the variant in the population.

Earlier this year, the FDA identified four EUA-authorized molecular tests that could be impacted by SARS-CoV-2 genetic variants, such as the B.1.1.7 variant that has been associated with an increased risk of transmission.^1-2

It is important to be aware that genetic variants are expected to continue to emerge in SARS-CoV-2, which can threaten the sensitivity of virtually any molecular test. This is due to the possibility that one of the targets is driving the sensitivity, so that even if the others still match perfectly the sensitivity can be reduced based on a mutation in a single target. By choosing a test that uses multiple genetic targets, a test will be less likely to be impacted by increased prevalence of genetic variants.³

How To Know If SARS-CoV-2 Variants Impact Your Molecular Test?

Consider the patterns of detection for your specific test. By choosing a test that uses multiple genetic targets, unfamiliar patterns may reveal the presence of new variants without impacting the final result of your test.

Stay up-to-date on emerging SARS-CoV-2 variants⁴, and their ability to evade detection by specific viral diagnostic tests.

Perform a repeat test. Per FDA recommendations⁵, consider negative results in combination with clinical observations, patient history and epidemiological information and repeat testing with a different test targeting different genetic regions if COVID-19 is still suspected.

How Do SARS-CoV-2 Molecular Tests Perform at the Point-of-Care?

All molecular tests used at the point-of-care are significantly faster than central-lab molecular tests 

Point-of-care molecular tests integrated with nucleic acid extraction are more sensitive than those without this crucial sample preparation step

Talis One provides rapid and accurate SARS-CoV-2 detection—quickly delivering central lab-quality results at the point of care

Confidently determine who needs to quarantine and be treated to achieve better patient outcomes with the Talis One COVID-19 Test. 

References

1. SARS-CoV-2 Viral Mutations: Impact on COVID-19 Tests. U.S. Food and Drug Administration website. Updated June 3, 2021. Accessed June 25, 2021. https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/sars-cov-2-viral-mutations-impact-covid-19-tests
2. Emergence of SARS-CoV-2 B.1.1.7 Lineage — United States. Centers for Disease Control and Prevention website. Updated January 22, 2021. Accessed June 25, 2021.https://www.cdc.gov/mmwr/volumes/70/wr/mm7003e2.htm
3. SARS-CoV-2 E Gene Variant Alters Analytical Sensitivity Characteristics of Viral Detection Using a Commercial Reverse Transcription-PCR Assay https://journals.asm.org/doi/full/10.1128/JCM.00075-21 Accessed August 12, 2021
4. Genetic Variants of SARS-CoV-2 May Lead to False Negative. U.S. Food and Drug Administration website. Updated March 30, 2021. Accessed June 25, 2021. https://www.fda.gov/medical-devices/letters-health-care-providers/genetic-variants-sars-cov-2-may-lead-false-negative-results-molecular-tests-detection-sars-cov-2
5. Science Brief: Emerging SARS-CoV-2 Variants. Centers for Disease Control and Prevention website. Updated January 28, 2021. Accessed June 25, 2021. https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/scientific-brief-emerging-variants.html
6. Manufacturers’ instructions for use accessed August 12, 2021 at https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-molecular-diagnostic-tests-sars-cov-2#individual-molecular
7. Subsoontorn, P., Lohitnavy, M. & Kongkaew, C. The diagnostic accuracy of isothermal nucleic acid point-of-care tests for human coronaviruses: A systematic review and meta-analysis. Sci Rep 10, 22349 (2020). https://doi.org/10.1038/s41598-020-79237-7 Accessed August 12, 2021