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.
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.
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.
So that we adhere to the strict rules around lateral flow tests, we have to make sure that anyone activating a sample pack is doing so purely to learn more about KnowNow Testing, and not as means of administering a clinical test.
The Limit of Detection (LoD) is the smallest amount of virus in a sample that a given device can consistently detect.
The Liverpool School of Tropical Medicine carried out an analytical study of the KnowNowᵀᴹ test, which determined that the LoD is 500 plaque-forming units per millilitre (PFU/ml). Based on accepted models of viral load in disease progression, this very low LoD suggests that the KnowNow test can detect infected people as early as day 3 to 4 of infection. This is before they become highly infectious, and a day or two earlier than most tests available.
In the absence of a single study that compares the LoD of KnowNowᵀᴹ to that of other tests, it is not possible to do a like-for-like comparison of the LoDs of different lateral flow tests determined by different studies. This is because there wouldn't be parity across cell cultures and strains of the virus used in the different studies. Additionally, it's important to consider that what the KnowNowᵀᴹ test detects is fundamentally different from other tests. KnowNowᵀᴹ is a true infectivity test which looks exclusively for the spike protein only present on active SARS-CoV-2 viruses. Whereas other lateral flow tests detect the nucleocapsid protein encapsulated in the centre of the virus, which can be present whether the virus is active or not.
The PFU/ml measure, as used in the Liverpool School of Tropical Medicine KnowNowᵀᴹ analytical study, is a measure of only the number of virus particles capable of forming plaques in a given sample - viral particles that are defective or which fail to infect their target cell will not produce a plaque and so are not counted by this measure. No inference can be made about the relationship of PFU to the overall number of viral particles in the sample, since this will differ from sample to sample.
Since the KnowNow test specifically detects infectious viral particles only, an LoD measured in PFU/ml is an informative and appropriate measure. However, for other lateral flow tests which indiscriminately detect active and inactive viral particles, an LoD referencing PFU/ml is not particularly informative or comparable to the KnowNowᵀᴹ LoD. For example, the sample used to determine LoD may have had a very low PFU/ml, but many inactive viral particles which were detected by the test. Ultimately, other lateral flow tests are not true tests for COVID infectivity, they do not detect only infectious virus like the KnowNowᵀᴹ test does.
If you'd like to read more about this subject, we recommend reading this paper. It argues that the "Limit of Detection matters and directly impacts efforts to identify, control, and contain outbreaks during this pandemic" since "higher LoD are likely to miss nonnegligible fractions of infected individuals." It also makes the case that LoD values for tests should be benchmarked against a universal standard and readily available in the public domain to enable like-for-like comparison of SARS-CoV-2 detection methods.
The KnowNowᵀᴹ Test and COVID-19 antibody tests test for completely different things.
Antibody tests identify whether someone has had coronavirus in the past, whereas the KnowNowᵀᴹ Test detects whether an individual is currently infectious.
Antibody testing involves detecting the immune response in the human body to having fought off a virus. These tests look for an antibody created in the bloodstream in response to the presence of a virus in that environment. This is useful when testing the effectiveness of a vaccine, or understanding how far and wide a virus has spread. However, it is of limited usefulness to individuals, as it is only able to identify whether an individual has fought off the SARS-CoV-2 virus in the past. It cannot effectively confirm whether they are currently infected, or infectious.
The KnowNowᵀᴹ test's unique detection mechanism identifies the infectiousness of the people tested. As a result, from our modelling based on accepted and peer-reviewed scientific literature, the KnowNowᵀᴹ test will detect asymptomatic people who are infectious with COVID-19.
The KnowNowᵀᴹ test has an impressively low limit of detection for an on-the-spot equipment-less test, of between 50,000 and 200,000 viral copies per mL, and so it is sensitive enough to identify infectious asymptomatic carriers even if they have low viral loads.
As the KnowNowᵀᴹ Test makes testing quicker, easier and more accessible, more people can get tested on an ongoing basis. Regular testing improves the chances of picking up asymptomatic carriers. Since the KnowNowᵀᴹ Test can detect the virus on day 3 to 4 after infection, based on KnowNow's low limit of detection and accepted models of viral load in disease progression, it identifies these carriers before they’re at a high risk of infecting other people.
Testing to identify asymptomatic carriers is so important, since they make up a large proportion of people who are infectious and enable the virus to keep spreading. 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.
The KnowNowᵀᴹ Test is the UK's only on-the-spot COVID-19 test that uses just your saliva to tell you if you are currently able to infect someone else with COVID-19.
Unlike other tests, the KnowNowᵀᴹ Test won't give you a positive result if you have been exposed to the SARS-CoV-2 virus in the past, but are no longer able to infect other people.
One box contains 25 tests, and measures 20cm (L) x 21cm (W) x 8cm (H).
COVID-19 test accuracy is typically determined by ‘specificity’ and ‘sensitivity’.
Specificity is about the extent to which you can eliminate false positives; sensitivity is how much virus needs to be present before a test picks it up. So there is always a need to strike a balance, when testing, between trying to pick up the virus as early as possible, versus accidentally delivering a positive test result for someone who is not actually infected.
The specificity of the KnowNowᵀᴹ Test is 99.9%. In more than 300 negative patient saliva samples, we haven’t had a single false positive.
What’s important when it comes to sensitivity is how much virus needs to be present in the patient sample for the test to give a positive signal. This is known as the 'Limit of Detection', and we measure this rather than clinical sensitivity as it is much more informative. Our Limit of Detection is between 50,000 and 200,000 viral copies per mL, making our test more sensitive than other rapid antigen tests available. The Abbott BinaxNow test, for example, needs 1,000,000 viral copies per mL in order to get a positive signal. The KnowNowᵀᴹ Test's very low Limit of Detection means it can detect infected people as early as day 3 to 4 of infection. This is before they become highly infectious, and a day or two earlier than most tests available (based on models of viral load in disease progression).
If you'd like to read more about this subject, we recommend this paper. It argues that the "Limit of Detection matters and directly impacts efforts to identify, control, and contain outbreaks during this pandemic" since "higher LoD are likely to miss nonnegligible fractions of infected individuals." It also makes the case that Limit of Detection values for tests using universal standard metrics should be readily available in the public domain to enable like-for-like comparison.
Used tests, swabs and buffer dropper tubes should be disposed of as potentially hazardous clinical waste.