Coronavirus (42) Mass asymptomatic testing of SARS-CoV-2 using lateral flow devices
In order to contain the spread of COVID-19, in addition to the national lockdown and nationwide COVID-19 vaccination, the UK government also use reverse-transcription polymerase chain reaction (RT-PCR) testing of nose/throat swabs, contact tracing procedures, and mobile applications to identify close contacts of infected symptomatic individuals.
In addition to the above measures, the government also rolled out mass asymptomatic testing on 9th April, aiming to identify people with COVID-19 who are not displaying any symptoms. This testing programme allows everyone in England to access two COVID-19 tests a week, free of charge, even if they do not have any symptoms.1 Ideally, by quickly identifying the asymptomatic patients and having these people self-isolate, and through the rapid finding and testing of their close contacts, the spread through the community could be interrupted.1
The programme uses the lateral flow test kit, SARS-CoV-2 Rapid Antigen Lateral Flow Qualitative Test, from Innova. Since many may have heard of the programme but not used the test kit, this and the coming blog posts provide more information about the test so that you can have a better idea of it.
What are lateral flow tests?
Lateral flow tests are basically assays designed to test for different protein targets. A sample is placed on a conjugation pad where the analyte (or antigen) of interest is bound by conjugated antibodies. The analyte-antibody mix then migrates along a membrane by capillary flow, across both ‘test’ and ‘control’ strips. These strips are coated with antibodies detecting the analyte of interest, and a positive test is confirmed by the appearance of coloured control and test lines.2
As no laboratory processing is needed, lateral flow tests can be performed in the area convenient to the person being tested. Moreover, a short turnaround time, relatively higher test accuracy and the economic affordability make the tests suitable for mass testing. In fact, the tests have been used for rapid testing in communities and workplaces.3
Innova SARS-CoV-2 Antigen Rapid Qualitative Test is a disposable test kit, like a home pregnancy test kit. It detects nucleocapsid protein antigen from SARS-CoV-2 in direct nose and/or throat swabs. A positive result is seen as a dark band or a fluorescent glow on the “test” strip after about 30 minutes.4 The appearance of two lines on both the “test” and “control” strips indicates that the test is positive. The appearance of one line on the “control” strip only indicates a negative result. However, if the “control” strip line does not appear after 30 minutes of waiting, this means the test has failed to work and should be retaken.
The whole procedure to perform the test by yourself is written clearly in the instruction booklet included in each pack of the test kit. It is interesting to find that, according to the instruction booklet distributed to NHS staff, NHS recommends only a nasal swab is used and the sample is taken in a different way to that described in the packaged instructions for use, with more rotation of the swab at a lower level of penetration, to enable easier self-administration of the test.5
Storage precautions
Test kits should be stored at room temperature. It is very important to keep the test kits in an area with no direct sunlight, neither should the test kit be kept in a fridge or freezer. High or low temperatures can denature or inactivate the antibodies in the kit and affect the result.
Instructions after knowing the results
If you are taking the lateral flow test at home, you should register the results, whether positive or negative, online or by calling 119. If you get a positive test result, everyone in your household must self-isolate according to the government guidelines.6 Moreover, you need to take an RT-PCR test to further confirm the result.1,6
If the test result is invalid, you need to retake the test with a new test kit.
References
1. Mass asymptomatic COVID-19 testing: Strategy and accuracy. Research briefing, House of Commons Library, 12 May, 2021. https://commonslibrary.parliament.uk/research-briefings/cbp-9223/
2. O'Farrell B. Evolution in lateral flow-based immunoassay systems. Lateral Flow Immunoass. 2009; p 1-33. https://doi.org/10.1007/978-1-59745-240-3_1.
3. Peto T & UK COVID-19 Lateral Flow Oversight Team. COVID-19: rapid antigen detection for SARS-CoV-2 by lateral flow assay: a national systematic evaluation for mass-testing. medRxiv. 2021; (published online Jan 26.) (preprint). https://doi.org/10.1101/2021.01.13.21249563
(Later published online in Lancet, May 29, 2021. DOI:https://doi.org/10.1016/j.eclinm.2021.100924)
4. Primary Care Supply webpage for Innova SARS-CoV-2 Antigen Rapid Qualitative Test. https://www.primarycaresupplies.co.uk/innova-sars-cov-2-antigen-lateral-flow-rapid-test-kit-box-of-20/
5. A guide for healthcare staff self-testing for coronavirus using a Lateral Flow Device (LFD). By NHS. https://www.england.nhs.uk/coronavirus/wp-content/uploads/sites/52/2020/11/LFD_NHSStaff_A4_161120_.pdf
6. Order coronavirus (COVID-19) rapid lateral flow tests. GOV.UK website. https://www.gov.uk/order-coronavirus-rapid-lateral-flow-tests
In order to contain the spread of COVID-19, in addition to the national lockdown and nationwide COVID-19 vaccination, the UK government also use reverse-transcription polymerase chain reaction (RT-PCR) testing of nose/throat swabs, contact tracing procedures, and mobile applications to identify close contacts of infected symptomatic individuals.
In addition to the above measures, the government also rolled out mass asymptomatic testing on 9th April, aiming to identify people with COVID-19 who are not displaying any symptoms. This testing programme allows everyone in England to access two COVID-19 tests a week, free of charge, even if they do not have any symptoms.1 Ideally, by quickly identifying the asymptomatic patients and having these people self-isolate, and through the rapid finding and testing of their close contacts, the spread through the community could be interrupted.1
The programme uses the lateral flow test kit, SARS-CoV-2 Rapid Antigen Lateral Flow Qualitative Test, from Innova. Since many may have heard of the programme but not used the test kit, this and the coming blog posts provide more information about the test so that you can have a better idea of it.
What are lateral flow tests?
Lateral flow tests are basically assays designed to test for different protein targets. A sample is placed on a conjugation pad where the analyte (or antigen) of interest is bound by conjugated antibodies. The analyte-antibody mix then migrates along a membrane by capillary flow, across both ‘test’ and ‘control’ strips. These strips are coated with antibodies detecting the analyte of interest, and a positive test is confirmed by the appearance of coloured control and test lines.2
As no laboratory processing is needed, lateral flow tests can be performed in the area convenient to the person being tested. Moreover, a short turnaround time, relatively higher test accuracy and the economic affordability make the tests suitable for mass testing. In fact, the tests have been used for rapid testing in communities and workplaces.3
Innova SARS-CoV-2 Antigen Rapid Qualitative Test is a disposable test kit, like a home pregnancy test kit. It detects nucleocapsid protein antigen from SARS-CoV-2 in direct nose and/or throat swabs. A positive result is seen as a dark band or a fluorescent glow on the “test” strip after about 30 minutes.4 The appearance of two lines on both the “test” and “control” strips indicates that the test is positive. The appearance of one line on the “control” strip only indicates a negative result. However, if the “control” strip line does not appear after 30 minutes of waiting, this means the test has failed to work and should be retaken.
The whole procedure to perform the test by yourself is written clearly in the instruction booklet included in each pack of the test kit. It is interesting to find that, according to the instruction booklet distributed to NHS staff, NHS recommends only a nasal swab is used and the sample is taken in a different way to that described in the packaged instructions for use, with more rotation of the swab at a lower level of penetration, to enable easier self-administration of the test.5
Storage precautions
Test kits should be stored at room temperature. It is very important to keep the test kits in an area with no direct sunlight, neither should the test kit be kept in a fridge or freezer. High or low temperatures can denature or inactivate the antibodies in the kit and affect the result.
Instructions after knowing the results
If you are taking the lateral flow test at home, you should register the results, whether positive or negative, online or by calling 119. If you get a positive test result, everyone in your household must self-isolate according to the government guidelines.6 Moreover, you need to take an RT-PCR test to further confirm the result.1,6
If the test result is invalid, you need to retake the test with a new test kit.
References
1. Mass asymptomatic COVID-19 testing: Strategy and accuracy. Research briefing, House of Commons Library, 12 May, 2021. https://commonslibrary.parliament.uk/research-briefings/cbp-9223/
2. O'Farrell B. Evolution in lateral flow-based immunoassay systems. Lateral Flow Immunoass. 2009; p 1-33. https://doi.org/10.1007/978-1-59745-240-3_1.
3. Peto T & UK COVID-19 Lateral Flow Oversight Team. COVID-19: rapid antigen detection for SARS-CoV-2 by lateral flow assay: a national systematic evaluation for mass-testing. medRxiv. 2021; (published online Jan 26.) (preprint). https://doi.org/10.1101/2021.01.13.21249563
(Later published online in Lancet, May 29, 2021. DOI:https://doi.org/10.1016/j.eclinm.2021.100924)
4. Primary Care Supply webpage for Innova SARS-CoV-2 Antigen Rapid Qualitative Test. https://www.primarycaresupplies.co.uk/innova-sars-cov-2-antigen-lateral-flow-rapid-test-kit-box-of-20/
5. A guide for healthcare staff self-testing for coronavirus using a Lateral Flow Device (LFD). By NHS. https://www.england.nhs.uk/coronavirus/wp-content/uploads/sites/52/2020/11/LFD_NHSStaff_A4_161120_.pdf
6. Order coronavirus (COVID-19) rapid lateral flow tests. GOV.UK website. https://www.gov.uk/order-coronavirus-rapid-lateral-flow-tests
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