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LFAs are currently rare, but due to their advantages of being quick and useable at the point of care, some healthcare professionals have suggested that as a format for antigen and antibody (serology) testing, they could positively change the testing landscape.<ref name="SheridanFast20">{{cite web |url=https://www.nature.com/articles/d41587-020-00010-2 |title=Fast, portable tests come online to curb coronavirus pandemic |author=Sheridan, C. |work=Nature Biotechnology - News |date=23 March 2020 |accessdate=08 April 2020 |doi=10.1038/d41587-020-00010-2}}</ref><ref name="BistriceanCOVID20">{{cite web |url=https://medium.com/@lablynx/covid-19-testing-for-the-physician-office-laboratory-pol-covidlims-com-bf1615e071ab |title=COVID-19 Testing for the Physician Office Laboratory (POL) - CovidLiMS.com |work=Medium |author=Bistricean, C. |date=01 April 2020 |accessdate=10 April 2020}}</ref><ref name="DickensCorona20">{{cite web |url=https://reaction.life/coronavirus-testing-how-it-works-questions-answered/ |title=Coronavirus testing: How it works – Questions answered |work=Reaction |author=Dickens, J.F. |date=03 April 2020 |accessdate=10 April 2020}}</ref> As of September 2021, 25 of 88 serology tests that have received EUAs by the FDA are explicitly labeled as being LFAs, with 12 of those 25 being approved for POC/CLIA-waived use.<ref name="FDAInVitroEUASero21">{{cite web |url=https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-serology-and-other-adaptive-immune-response-tests-sars-cov-2 |title=In Vitro Diagnostics EUAs - Serology and Other Adaptive Immune Response Tests for SARS-CoV-2 |publisher=U.S. Food and Drug Administration |date=03 September 2021 |accessdate=07 September 2021}}</ref> An article by Sheridan in ''Nature Biotechnology'' highlights a handful of others developed around the world (see their Table 1).<ref name="SheridanFast20" /> FIND shows more than 400 commercialized rapid diagnostic immunoassay tests around the world, though it's not clear how many of them actually LFAs (from their list, only 14 are explicitly stated as being LFA).<ref name="FINDSARS20">{{cite web |url=https://www.finddx.org/covid-19/pipeline/ |title=SARS-CoV-2 Diagnostic Pipeline |author=Foundation for Innovative New Diagnostics |publisher=Foundation for Innovative New Diagnostics |date=n.d. |accessdate=18 November 2020}}</ref> While LFAs have increasingly been approved around the world in 2021<ref name="FDAInVitroEUASero21" /><ref name="FINDSARS20" />, it remains a question whether or not we continue to see more of them, at least in the United States.<ref name="BistriceanCOVID20" />
[[File:Blood in tubes (9617266704).jpg|left|250px]]Blood serum or serology assays come in three common varieties: LFA, enzyme-linked immunosorbent assay (ELISA), or neutralization assay.<ref name="JHSerology20">{{cite web |url=https://www.centerforhealthsecurity.org/covid-19TestingToolkit/serology/Serology-based-tests-for-COVID-19.html |title=Serology tests for COVID-19 |author=Center for Health Security |publisher=Johns Hopkins University |date=26 August 2021 |accessdate=06 September 2021}}</ref> As discussed prior, LFAs are intended to be rapid point-of-care tools for qualitatively testing body fluids for patient antibodies or viral antigen. The ELISA is, in contrast, a more lab-bound method which produces results that are qualitative or quantitative. In the context of COVID-19 testing, ELISA tests for the presence of patient antibodies in a given specimen based upon whether or not an interaction is observed with the viral proteins present on the test plate. However, even if antibodies are present, ELISA isn't able to tell a clinician if those antibodies are able to protect against future infection. Neutralization assays are the lengthiest to complete, taking from three upwards to five days.<ref name="JHSerology20" /> This is largely due to the fact that the assay depends on culturing cells that encourage growth of the target virus. Afterwards, introduced patient antibodies, if present, will fight to prevent viral infection of cells. This process is performed in decreasing concentrations, giving the clinician an opportunity to "visualize and quantify how many antibodies in the patient serum are able to block virus replication."<ref name="JHSerology20" /> In contrast to ELISA, a neutralization assay is able to determine if a patient's antibodies are actively fighting against the target virus, even after recovering from the infection. In November 2020, the FDA granted an EUA to the first ELISA-based serology test to detect nuetralizing antibodies from recent or prior SARS-CoV-2 infection.<ref name="FDACoronaNeut20">{{cite web |url=https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-test-detects-neutralizing-antibodies-recent-or |title=Coronavirus (COVID-19) Update: FDA Authorizes First Test that Detects Neutralizing Antibodies from Recent or Prior SARS-CoV-2 Infection |author=Food and Drug Administration |publisher=Food and Drug Administration |date=06 November 2020 |accessdate=18 November 2020}}</ref>


Also of note are [[Variants of PCR#Isothermal amplification methods|isothermal amplification]] methods. Abbott's ID NOW and Cue Health's Cue COVID-19 and Cue COVID-19 Test for Home and OTC tests (the latter being the first isothermal amplification test approved for home use) are described by the FDA as using "isothermal nucleic acid amplification technology for the qualitative detection of SARS-CoV-2 viral nucleic acids."<ref name="HintonCue20">{{cite web |url=https://www.fda.gov/media/136522/download |format=PDF |title=ID NOW COVID-19 |author=Hinton, D.M. |publisher=U.S. Food and Drug Administration |date=27 March 2020 |accessdate=10 April 2020}}</ref><ref name="HintonIDNOW20">{{cite web |url=https://www.fda.gov/media/138823/download |format=PDF |title=Cue COVID-19 Test |author=Hinton, D.M. |publisher=U.S. Food and Drug Administration |date=10 June 2020 |accessdate=08 July 2020}}}}</ref><ref name="HintonCueOTC21">{{cite web |url=https://www.fda.gov/media/146467/download |format=PDF |title=Cue COVID-19 Test for Home and Over The Counter (OTC) Use |author=Hinton, D.M. |publisher=U.S. Food and Drug Administration |date=05 March 2021 |accessdate=07 September 2021}}</ref> Isothermal amplification tends to be an easier process to manage due to being able to keep amplification at a constant temperature.<ref name="ZanoliIsotherm13">{{cite journal |title=Isothermal Amplification Methods for the Detection of Nucleic Acids in Microfluidic Devices |journal=Biosensors |author=Zanoli, L.M.; Spoto, G. |volume=3 |issue=1 |pages=18–43 |year=2013 |doi=10.3390/bios3010018 |pmid=25587397 |pmc=PMC4263587}}</ref> In fact, Abbott has stated its EUAed ID NOW COVID-19 test can be completed within five minutes.<ref name="AbbottDetect20">{{cite web |url=https://www.abbott.com/corpnewsroom/product-and-innovation/detect-covid-19-in-as-little-as-5-minutes.html |title=Detect COVID-19 in as Little as 5 Minutes |publisher=Abbott |date=27 March 2020 |accessdate=10 April 2020}}</ref> However, May 2020 findings by New York University put the test's accuracy into question. On July 1, 2020, an FDA spokesperson allegedly indicated receipt of 126 reports of "adverse events" concerning the test.<ref name="DevineCorona20">{{cite web |url=https://www.cnn.com/2020/07/03/politics/coronavirus-white-house-test-abbott/index.html |title=Coronavirus test used by White House has questionable accuracy |author=Devine, C. |work=CNN Politics |date=03 July 2020 |accessdate=08 July 2020}}</ref> In 2020, some 393 complaints were reported to the FDA, with 1,492 complains being reported in 2021 (through July 31) according to an FDA MAUDE (Manufacturer and User Facility Device Experience) search.<ref name="FDAMAUDE">{{cite web |url=https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/Search.cfm |title=MAUDE - Manufacturer and User Facility Device Experience |publisher=U.S. Food and Drug Administration |accessdate=07 September 2021 |quote=Search for "ID NOW COVID-19" in Brand Name}}</ref> The FDA was reportedly investigating the data and working with Abbott to have additional studies performed on the test's accuracy in 2020.<ref name="PerroneFDA20">{{cite web |url=https://apnews.com/c8ab010e8e02dfe7beb34a5e5df11279 |title=FDA probes accuracy issue with Abbott’s rapid virus test |author=Perrone, M. |work=Associated Press |date=14 May 2020 |accessdate=19 May 2020}}</ref> In October 2020, Abbott released additional study data showing overall sensitivity of 93.3% and specificity of 98.4%, emphasizing the ID NOW's best use with samples taken within seven days of symptom onset.<ref name="TaylorAbbot20">{{cite web |url=https://www.medtechdive.com/news/abbott-on-defense-id-now-coronavirus-test-postmarket-study/586579/ |title=Abbott, on defense, details embattled rapid COVID-19 test results |author=Taylor, N.P. |work=MedTechDive |date=07 October 2020 |accessdate=18 November 2020}}</ref> On August 27, 2021, the FDA re-issued its EUA for the ID NOW with updated ''in silico'' inclusivity analysis results (among other things)<ref name="HintonIDNOWAug21">{{cite web |url=https://www.fda.gov/media/136522/download |format=PDF |title=ID NOW COVID-19 |author=Hinton, D.M. |publisher=U.S. Food and Drug Administration |date=27 August 2021 |accessdate=07 September 2021}}</ref>, but it's not clear if the FDA is continuing to work with Abbott on the test's accuracy claims.
Johns Hopkins' Center for Health Security [https://www.centerforhealthsecurity.org/covid-19TestingToolkit/serology/Serology-based-tests-for-COVID-19.html appears to be tracking] serology-based COVID-19 tests that are in development or have been approved in various parts of the globe. However, for the most up-to-date list of serology tests that have received EUAs in the United States, the FDA's [https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-serology-and-other-adaptive-immune-response-tests-sars-cov-2 EUA list] appears to be the best source. As of September 2021, the FDA shows 88 serology assays approved for diagnostic use in the U.S. Of those 88, sixteen are explicitly listed as being ELISA-based.


Specific isothermal amplification techniques called [[loop-mediated isothermal amplification]] (LAMP) and reverse transcription LAMP (RT-LAMP) are beginning to emerge as options for COVID-19 testing. For example, Talis Biomedical is developing the Talis One COVID-19 system for point-of-care testing. It has received National Institutes of Health's Rapid Acceleration of Diagnostics (RADx) funding<ref name="NIHDelivering20">{{cite web |url=https://www.nih.gov/news-events/news-releases/nih-delivering-new-covid-19-testing-technologies-meet-us-demand |title=NIH delivering new COVID-19 testing technologies to meet U.S. demand |author=National Institutes of Health |publisher=National Institutes of Health |work=News Releases |date=31 July 2020 |accessdate=12 August 2020}}</ref> and, should it receive its EUA (as of August 2021, it was still awaiting FDA authorization<ref name="O'ConnorDespite21">{{cite web |url=https://www.360dx.com/business-news/despite-mdx-product-delays-talis-biomedical-expecting-meaningful-revenue-ramp-2022 |archiveurl=https://web.archive.org/web/20210811210316/https://www.360dx.com/business-news/despite-mdx-product-delays-talis-biomedical-expecting-meaningful-revenue-ramp-2022 |title=Despite MDx Product Delays, Talis Biomedical Expecting 'Meaningful Revenue Ramp in 2022' |author=O'Connor, L. |work=360 Dx |date=11 August 2021 |archivedate=11 August 2021 |accessdate=07 September 2021}}</ref>), is expected to be among the first U.S.-approved RT-LAMP tests for COVID-19.<ref name="TalisOne">{{cite web |url=https://talis.bio/technology/ |title=The Talis Advantage |publisher=Talis Biomedical |accessdate=13 August 2020}}</ref> In November 2020, the first LAMP-based, prescription "collect and test" at-home kit—the Lucira COVID-19 All-In-One Test Kit—was approved by the FDA for emergency use.<ref name="RomoFDAApproves20">{{cite web |url=https://www.npr.org/sections/coronavirus-live-updates/2020/11/17/936055284/fda-approves-first-at-home-coronavirus-test |title=FDA Approves 1st At-Home Coronavirus Test |author=Romo, V. |work=NPR |date=17 November 2020 |accessdate=18 November 2020}}</ref> Globally, examining FIND's list of nearly 280 commercialized manual NAAT tests around the world, five of them are explicitly shown to be some form of LAMP test. Multiple preprints on ''medRxiv'' and ''bioRxiv'', as well as published papers, suggest that RT-LAMP could provide rapid results for SARS-CoV-2 testing.<ref name="Schmid-BurgkLAMP20">{{cite journal |title=LAMP-Seq: Population-Scale COVID-19 Diagnostics Using Combinatorial Barcoding |journal=bioRxiv |author=Schmid-Burgk, J.L.; Li, D.; Feldman, D. et al. |year=2020 |doi=10.1101/2020.04.06.025635}}</ref><ref name="LambRapid20">{{cite journal |title=Rapid Detection of Novel Coronavirus (COVID-19) by Reverse Transcription-Loop-Mediated Isothermal Amplification |journal=medRxiv |author=Lamb, L.E.; Barolone, S.N.; Ward, E. et al. |year=2020 |doi=10.1101/2020.02.19.20025155}}</ref><ref name="KellnerARapid20">{{cite journal |title=A rapid, highly sensitive and open-access SARS-CoV-2 detection assay for laboratory and home testing |journal=bioRxiv |author=Kellner, M.J.; Ross, J.J.; Schnabl, J. et al. |year=2020 |doi=10.1101/2020.06.23.166397}}</ref><ref name="YuRapid20">{{cite journal |title=Rapid Detection of COVID-19 Coronavirus Using a Reverse Transcriptional Loop-Mediated Isothermal Amplification (RT-LAMP) Diagnostic Platform |journal=Clinical Chemistry |author=Yu, L.; Wu, S.; Hao, X. et al. |volume=66 |issue=7 |pages=975–77 |year=2020 |doi=10.1093/clinchem/hvaa102 |pmid=32315390 |pmc=PMC7188121}}</ref><ref name="ParkDevelop20">{{cite journal |title=Development of Reverse Transcription Loop-Mediated Isothermal Amplification Assays Targeting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) |journal=Journal of Molecular Diagnostics |author=Park, G.-S.; Ku, K.; Baek, S.-H. et al. |volume=22 |issue=6 |pages=729–35 |year=2020 |doi=10.1016/j.jmoldx.2020.03.006 |pmid=32276051 |pmc=PMC7144851}}</ref> However, it's apparent that adoption of LAMP as a COVID-19 test technique has been slow at best overall.
A review of Johns Hopkins' tracking list showed more LFA-based tests among those approved in other parts of the world. Among their list of those still in development, an LFA stands out for integrating CRISPR detection.<ref name="MBAProto20">{{cite web |url=https://mammoth.bio/wp-content/uploads/2020/03/Mammoth-Biosciences-A-protocol-for-rapid-detection-of-SARS-CoV-2-using-CRISPR-diagnostics-DETECTR.pdf |format=PDF |title=A protocol for rapid detection of the 2019 novel coronavirus SARS-CoV-2 using CRISPR diagnostics: SARS-CoV-2 DETECTR |publisher=Mammoth Biosciences |date=02 March 2020 |accessdate=09 April 2020}}</ref> CRISPR (clustered regularly interspaced short palindromic repeats) represents bacterial and archaeal DNA sequences derived from DNA fragments of previous infection. This genetic material can then be used as an activator of biomarkers when attached RNA "guides" find a match with target viral RNA in patient specimen.<ref name="NatureCRISPR18">{{cite web |url=https://www.nature.com/articles/d41586-018-02200-0 |title=CRISPR’s powers unleashed for disease detection |work=Nature - Research Highlights |date=16 February 2018 |accessdate=09 April 2020}}</ref> This CRISPR-based LFA, called DETECTR, was further described in a paper published in October 2020, with the authors concluding it could be used "as a complementary technically independent approach to qRT-PCR, thereby increasing the testing capacity of medical microbiological laboratories and relieving the existent PCR-platforms for routine non-SARS-CoV-2 diagnostic testing."<ref name="BrandsmaRapid20">{{cite journal |title=Rapid, sensitive and specific SARS coronavirus-2 detection: A multi-center comparison between standard qRT-PCR and CRISPR based DETECTR |journal=The Journal of Infectious Diseases |author=Brandsma, E.; Verhagen, H.J.M.P.; van de Laar, T.J.W. et al. |volume=In Print |at=jiaa641 |year=2020 |doi=10.1093/infdis/jiaa641 |pmid=33038252 |pmc=PMC7665660}}</ref>


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

Revision as of 18:29, 3 February 2022

Blood in tubes (9617266704).jpg

Blood serum or serology assays come in three common varieties: LFA, enzyme-linked immunosorbent assay (ELISA), or neutralization assay.[1] As discussed prior, LFAs are intended to be rapid point-of-care tools for qualitatively testing body fluids for patient antibodies or viral antigen. The ELISA is, in contrast, a more lab-bound method which produces results that are qualitative or quantitative. In the context of COVID-19 testing, ELISA tests for the presence of patient antibodies in a given specimen based upon whether or not an interaction is observed with the viral proteins present on the test plate. However, even if antibodies are present, ELISA isn't able to tell a clinician if those antibodies are able to protect against future infection. Neutralization assays are the lengthiest to complete, taking from three upwards to five days.[1] This is largely due to the fact that the assay depends on culturing cells that encourage growth of the target virus. Afterwards, introduced patient antibodies, if present, will fight to prevent viral infection of cells. This process is performed in decreasing concentrations, giving the clinician an opportunity to "visualize and quantify how many antibodies in the patient serum are able to block virus replication."[1] In contrast to ELISA, a neutralization assay is able to determine if a patient's antibodies are actively fighting against the target virus, even after recovering from the infection. In November 2020, the FDA granted an EUA to the first ELISA-based serology test to detect nuetralizing antibodies from recent or prior SARS-CoV-2 infection.[2]

Johns Hopkins' Center for Health Security appears to be tracking serology-based COVID-19 tests that are in development or have been approved in various parts of the globe. However, for the most up-to-date list of serology tests that have received EUAs in the United States, the FDA's EUA list appears to be the best source. As of September 2021, the FDA shows 88 serology assays approved for diagnostic use in the U.S. Of those 88, sixteen are explicitly listed as being ELISA-based.

A review of Johns Hopkins' tracking list showed more LFA-based tests among those approved in other parts of the world. Among their list of those still in development, an LFA stands out for integrating CRISPR detection.[3] CRISPR (clustered regularly interspaced short palindromic repeats) represents bacterial and archaeal DNA sequences derived from DNA fragments of previous infection. This genetic material can then be used as an activator of biomarkers when attached RNA "guides" find a match with target viral RNA in patient specimen.[4] This CRISPR-based LFA, called DETECTR, was further described in a paper published in October 2020, with the authors concluding it could be used "as a complementary technically independent approach to qRT-PCR, thereby increasing the testing capacity of medical microbiological laboratories and relieving the existent PCR-platforms for routine non-SARS-CoV-2 diagnostic testing."[5]

References

  1. ↑ 1.0 1.1 1.2 Center for Health Security (26 August 2021). "Serology tests for COVID-19". Johns Hopkins University. https://www.centerforhealthsecurity.org/covid-19TestingToolkit/serology/Serology-based-tests-for-COVID-19.html. Retrieved 06 September 2021. 
  2. ↑ Food and Drug Administration (6 November 2020). "Coronavirus (COVID-19) Update: FDA Authorizes First Test that Detects Neutralizing Antibodies from Recent or Prior SARS-CoV-2 Infection". Food and Drug Administration. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-test-detects-neutralizing-antibodies-recent-or. Retrieved 18 November 2020. 
  3. ↑ "A protocol for rapid detection of the 2019 novel coronavirus SARS-CoV-2 using CRISPR diagnostics: SARS-CoV-2 DETECTR" (PDF). Mammoth Biosciences. 2 March 2020. https://mammoth.bio/wp-content/uploads/2020/03/Mammoth-Biosciences-A-protocol-for-rapid-detection-of-SARS-CoV-2-using-CRISPR-diagnostics-DETECTR.pdf. Retrieved 09 April 2020. 
  4. ↑ "CRISPR’s powers unleashed for disease detection". Nature - Research Highlights. 16 February 2018. https://www.nature.com/articles/d41586-018-02200-0. Retrieved 09 April 2020. 
  5. ↑ Brandsma, E.; Verhagen, H.J.M.P.; van de Laar, T.J.W. et al. (2020). "Rapid, sensitive and specific SARS coronavirus-2 detection: A multi-center comparison between standard qRT-PCR and CRISPR based DETECTR". The Journal of Infectious Diseases In Print: jiaa641. doi:10.1093/infdis/jiaa641. PMC PMC7665660. PMID 33038252. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7665660. 
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