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Another method some labs are taking to speed up turnaround time is using pooled testing. The general concept involves placing two or more test specimens together and testing the pool as one specimen. The most obvious advantage to this is that the process saves on reagents and other supplies, particularly when supply chains are disrupted, and it reduces the amount of time required to analyze large quantities of specimens.<ref name="CDCInterimPool21">{{cite web |url=https://www.cdc.gov/coronavirus/2019-ncov/lab/pooling-procedures.html |title=Interim Guidance for Use of Pooling Procedures in SARS-CoV-2 Diagnostic and Screening Testing |author=Centers for Disease Control and Prevention |publisher=Centers for Disease Control and Prevention |date=30 June 2021 |accessdate=19 September 2021}}</ref> This methodology is best used "in situations where disease prevalence is low, since each negative pool test eliminates the need to individually test those specimens and maximizes the number of individuals who can be tested over a given amount of time."<ref name="RohdeCOVID20">{{cite web |url=https://asm.org/Articles/2020/July/COVID-19-Pool-Testing-Is-It-Time-to-Jump-In |title=COVID-19 Pool Testing: Is It Time to Jump In? |author=Rohde, R. |publisher=American Society for Microbiology |date=20 July 2020 |accessdate=06 August 2020}}</ref> However, it's best left to situations where expectations are that less than 10 percent of the population being tested is affected by what's being tested for.<ref name="RohdeCOVID20" /><ref name="MashaPooled20">{{cite web |url=https://asiatimes.com/2020/08/pooled-virus-tests-help-stretched-health-services/ |title=Pooled virus tests help stretched health services |author=Masha, M.; Chau, S. |work=Asia Times |date=04 August 2020 |accessdate=06 August 2020}}</ref><ref name="CitronerHowPool20">{{cite web |url=https://www.healthline.com/health-news/how-pooled-testing-can-help-us-fight-spread-of-covid-19 |title=How Pooled Testing Can Help Us Fight Spread of COVID-19 |author=Citroner, G. |work=Healthline |date=03 August 2020 |accessdate=06 August 2020}}</ref>
As mentioned in the previous chapter, the benefits of antigen testing For COVID-19 and other viral infections are 1. specimen collection can typically be done with a simple nasal swab rather than a more invasive [[nasopharyngeal swab]], 2. testing is more rapid and convenient, and 3. it takes some pressure off the PCR supply chain. However, antigen testing only tests what's there, rather than amplifying the amount, resulting in generally lower sensitivities.<ref name="ServiceRadical2020">{{cite journal |title=Radical shift in COVID-19 testing needed to reopen schools and businesses, researchers say |journal=Science |author=Service, R.F. |year=2020 |doi=10.1126/science.abe1546}}</ref><ref name="GuglielmiTheExp20">{{cite journal |title=The explosion of new coronavirus tests that could help to end the pandemic |journal=Nature |author=Guglielmi, G. |volume=583 |pages=506–09 |year=2020 |doi=10.1038/d41586-020-02140-8}}</ref> As such, the real utility of antigen testing, despite its lower sensitivity, appears to be surveillance situations where a large group of individuals who are at risk can be screened at regularly scheduled intervals of two to four days. If your lab is able to support this sort of testing, then this type of testing may be an option. As of September 2021, thirty-four FDA EUAs for antigen tests have been issues; 28 of those 34 include allowances for CLIA-waived testing, and 10 were authorized for home use.<ref name="FDAInVitroAntigen21">{{cite web |url=https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-antigen-diagnostic-tests-sars-cov-2 |title=In Vitro Diagnostics EUAs - Antigen Diagnostic Tests for SARS-CoV-2 |publisher=U.S. Food and Drug Administration |date=07 September 2021 |accessdate=07 September 2021}}</ref> Review [https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-antigen-diagnostic-tests-sars-cov-2 the FDA list] to further examine your options.


The downside of pooled testing comes with the issues of dilution, contamination, and populations with 10 or more percent infected. A target-positive specimen that commingles with other target-free specimens is itself diluted and in some cases may cause issues with the limit of detection for the assay. Additionally, if the pool tests positive, target-free specimens may become contaminated by a target-positive specimen. This may cause issues with any individual specimen assays that get ran. And the workflows involving pooling must be precise, as a technician working with multiple specimens at the same time increases the chance of lab errors.<ref name="RohdeCOVID20" /><ref name="MashaPooled20" /><ref name="CitronerHowPool20" /> Finally, at least in the U.S., a Food and Drug Administration (FDA) emergency use authorization (EUA) for a validated pooled testing method is required.<ref name="RohdeCOVID20" /> (Validation of pooled methods may differ in other countries.<ref name="MashaPooled20" />) The U.S. Centers for Disease Control and Prevention (CDC) has published [https://www.cdc.gov/coronavirus/2019-ncov/lab/pooling-procedures.html interim guidance] on pooled testing strategies for [[SARS-CoV-2]].
The CDC emphasizes that molecular testing remains the "gold standard" for detecting SARS-CoV-2 in a sample, and it "may be necessary to confirm an antigen test result with a laboratory-based NAAT, especially if the result of the antigen test is inconsistent with the clinical context." However, some molecular tests designed for point-of-care testing may not be sufficiently designed for confirmatory testing; consult the instructions for use for any confirmatory test.<ref name="CDCInterim21">{{cite web |url=https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html |title=Interim Guidance for Antigen Testing for SARS-CoV-2 |author=Centers for Disease Control and Prevention |publisher=Centers for Disease Control and Prevention |date=09 September 2021 |accessdate=18 September 2021}}</ref> The CDC [https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html#anchor_1631295114633 makes available] two antigen testing algorithms for determining when confirmatory testing is actually recommended.<ref name="CDCInterim21" />
 
On April 20, 2021, the FDA updated its policies to allow for pooled testing to be added to the use case scenarios for several existing test kits. "This means that tests with EUAs that are amended by this authorization may be used with pooled anterior nasal specimens from individuals without known or suspected COVID-19 when such individuals are tested as part of a testing program that includes testing at regular intervals, at least once per week."<ref name="FDAInVitroEUAs21">{{cite web |url=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 |title=In Vitro Diagnostics EUAs - Molecular Diagnostic Tests for SARS-CoV-2 |publisher=U.S. Food and Drug Administration |date=07 September 2021 |accessdate=07 September 2021}}</ref> However, affected kits can only be used in high-complexity CLIA labs, though "tests authorized for use in specific named or designated high-complexity laboratories can only be used in such laboratories."<ref name="FDAInVitroEUAs21" /> As of September 2021, four PCR test kit EUAs were amended to allow for pooled testing<ref name="FDAInVitroEUAs21" />:
 
* Biomeme SARS-CoV-2 Real-Time RT-PCR Test
* Clinical Enterprise SARS-SoV-2-RT-PCR Assay
* CRSP SARS-CoV-2 Real-time Reverse Transcriptase (RT)-PCR Diagnostic Assay (Version 3)
* Viracor SARS-CoV-2 assay


==References==
==References==
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{{Reflist|colwidth=30em}}

Revision as of 19:19, 3 February 2022

As mentioned in the previous chapter, the benefits of antigen testing For COVID-19 and other viral infections are 1. specimen collection can typically be done with a simple nasal swab rather than a more invasive nasopharyngeal swab, 2. testing is more rapid and convenient, and 3. it takes some pressure off the PCR supply chain. However, antigen testing only tests what's there, rather than amplifying the amount, resulting in generally lower sensitivities.[1][2] As such, the real utility of antigen testing, despite its lower sensitivity, appears to be surveillance situations where a large group of individuals who are at risk can be screened at regularly scheduled intervals of two to four days. If your lab is able to support this sort of testing, then this type of testing may be an option. As of September 2021, thirty-four FDA EUAs for antigen tests have been issues; 28 of those 34 include allowances for CLIA-waived testing, and 10 were authorized for home use.[3] Review the FDA list to further examine your options.

The CDC emphasizes that molecular testing remains the "gold standard" for detecting SARS-CoV-2 in a sample, and it "may be necessary to confirm an antigen test result with a laboratory-based NAAT, especially if the result of the antigen test is inconsistent with the clinical context." However, some molecular tests designed for point-of-care testing may not be sufficiently designed for confirmatory testing; consult the instructions for use for any confirmatory test.[4] The CDC makes available two antigen testing algorithms for determining when confirmatory testing is actually recommended.[4]

References

  1. ↑ Service, R.F. (2020). "Radical shift in COVID-19 testing needed to reopen schools and businesses, researchers say". Science. doi:10.1126/science.abe1546. 
  2. ↑ Guglielmi, G. (2020). "The explosion of new coronavirus tests that could help to end the pandemic". Nature 583: 506–09. doi:10.1038/d41586-020-02140-8. 
  3. ↑ "In Vitro Diagnostics EUAs - Antigen Diagnostic Tests for SARS-CoV-2". U.S. Food and Drug Administration. 7 September 2021. https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-antigen-diagnostic-tests-sars-cov-2. Retrieved 07 September 2021. 
  4. ↑ 4.0 4.1 Centers for Disease Control and Prevention (9 September 2021). "Interim Guidance for Antigen Testing for SARS-CoV-2". Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html. Retrieved 18 September 2021. 
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