There have been questions raised around the sensitivity of rapid lateral flow antigen testing for SARS-CoV-2 as compared to PCR testing. However, these questions have been strongly challenged by the scientific community.
PCR tests identify the presence of the SARS-CoV-2 virus in the body, regardless of whether the virus is actively infectious. The PCR testing process amplifies the genetic code of the virus so that even minuscule amounts of the virus in the sample can be picked up. This makes for a powerful test, but since viral fragments can linger in the body for weeks even after the infection has cleared, infected individuals being tested using PCR will show as positive for a median period of 22–33 days in total. On the other hand, most people infected with SARS-CoV-2 are contagious only for 4–8 days.
So whilst PCR testing for SARS-CoV-2 may have been considered the "gold standard" test up until now, it will by definition show different results when compared to lateral flow tests which aim to identify individuals based on viral loads which suggest they are within their infectious window. This discrepancy between what each test is actually testing for has caused some issues where PCR testing has been used to evaluate the effectiveness of lateral flow tests, such as in the mass testing rolled out in Liverpool in November 2020.
The KnowNowᵀᴹ Test goes a step beyond other lateral flow tests with its unique, patented detection mechanism which only shows a positive result when live infectious virus is identified in the sample. As a result, PCR tests will similarly show different results to the KnowNowᵀᴹ Test in certain cases, since they will show positive results even for individuals outside of their infectious period.
For a much more comprehensive and referenced answer, you may like to read "Clarifying the evidence on SARS-CoV-2 antigen rapid tests in public health responses to COVID-19" from the Lancet.
The KnowNowᵀᴹ test will provide a result within 17-18 minutes of an individual arriving for their test.
The process of taking the saliva sample, mixing it with the buffer solution and dropping it onto the KnowNow test device should take a clinical professional no more than 2 to 3 minutes.
It then takes just 15 minutes for the test result to develop in the KnowNow device test results window.
The test result should not be read and interpreted after 60 minutes. If it wasn't possible to read and interpret the results between 15 and 60 minutes after dropping the solution into the sample well, the test should be discarded and the process repeated with another new test and saliva sample.
Receiving a negative result means that the individual tested does not have any live virus in the sample provided and is not currently infectious to others. However, it's important to be aware that they could still be exposed to the SARS-CoV-2 virus following the test. It could also be possible that the individual tested has already been exposed to the virus 1 or 2 days ago, and they have not yet become infectious to others.
As a result, we recommend that individuals are tested as regularly as possible to keep workplaces and communities safe. Depending on the scenario, we would recommend testing is repeated every 1 to 3 days.
If there is one red line visible next to the "C" in the KnowNow device test results window, and no line at all next to the "T", then the test result is negative. This indicates that no SARS-CoV-2 antigen has been detected in the sample.
SARS-CoV-2 is able to spread from individuals who are pre-symptomatic or asymptomatic. As a result, testing and isolation based on symptoms alone will not be sufficient to stop the spread.
This narrative review of 16 clinical studies around the globe concludes that between 40-45% of those infected with SARS-CoV-2 never develop symptoms, and that these asymptomatic carriers can infect others for an extended period, perhaps longer than 14 days.
Regular community testing with a rapid antigen test like the KnowNowᵀᴹ Test to identify asymptomatic, but infectious, individuals offers one way to break the chain of transmission and enable the re-opening of societies.
To date we have conducted three clinical studies. The first was a UK Government-supported National Institute for Health Research (NIHR) study across ten UK hospitals; the second was with Liverpool School of Tropical Medicine, and the third is a community study that we have led ourselves. We have also carried out our own analytical assessments, as well as two Public Health England analytical assessments.
We have worked with over 280 negative patient samples and around 100 COVID-19 positive patients across our studies. We are also currently carrying out a 650+ patient clinical trial with sites in the UK, USA and Brazil to provide us with a higher volume of clinical data, and with a view to additional regulatory approvals to widen the reach of the impact we can have globally in pandemic recovery.
KnowNowᵀᴹ offers two key benefits over polymerase chain reaction (PCR) tests.
The first benefit is that the KnowNowᵀᴹ test needs only a saliva sample, which can be taken easily and comfortably from the mouth. PCR tests usually need a nasopharyngeal, anterior nasal or tonsil sample, all of which are painful and unpleasant for the individual being tested and more challenging to collect effectively for the clinical professional administering the test. No one wants to be made to cry or gag, or make someone else cry or gag, on a regular basis!
The second benefit is that the KnowNow test uses its unique detection mechanism to determine whether an individual is actually infectious, whereas PCR tests identify whether SARS-CoV-2 viral matter is present in an individual's body, regardless of whether it is already inactive.
Although PCR tests have been seen as the "gold standard" test for the SARS-CoV-2 virus, they do have a number of drawbacks. Laboratory processing is required, meaning that there is a delay before results can be returned, and the associated costs are relatively high. Also the detection mechanism does not specifically identify whether individuals are infectious. In fact, PCR tests detect the virus long after the infectious period, and individuals can continue to test positive for a mean of 17 days after they have stopped being able to infect others (source). This means that people who are not infectious are unnecessarily quarantined as a result of a positive PCR test.
We recommend that individuals are tested as regularly as possible to keep workplaces, venues and communities safe.
It is important to remember that individuals can still go on to be exposed to the virus following a negative test result. Additionally, a high proportion of infectious people show no symptoms at all, and so regular testing is key to breaking the chain of transmission.
Depending on the scenario, we would recommend that testing is performed every 2-3 days, or daily, depending on the scenario.
We’re focused on developing our predictive health technology and tests so that we can make medicine more proactive and help to predict illness before it becomes acute or infectious. We want to empower people to feel in charge of their own health and wellbeing by making testing more readily accessible and available, allowing for earlier prediction and prevention of acute illnesses.
A lateral flow test is a simple diagnostic device designed to detect the presence or absence of a target substance in a liquid sample without the need for specialised and costly equipment.
The most commonly recognised type of lateral flow rapid test strip is the pregnancy test.
One box contains 25 tests, and measures 20cm (L) x 21cm (W) x 8cm (H).
The space required depends on how many tests you require at any given time. However, as the KnowNowᵀᴹ Tests can be stored at any temperature between 2 and 30 degrees, special storage facilities should not be required in the UK, unless there is unusually hot weather.