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 100%. In more than 700 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.
The adjective "vatic" means "describing or predicting what will happen in the future," and derives directly from the Latin word vates, meaning "seer" or "prophet."
We chose this name as it speaks to our mission to make healthcare more proactive and empowering, through predictive screening for acute disease.
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.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the name given by the International Committee on Taxonomy of Viruses (ICTV) to the virus responsible for causing the disease, COVID-19.
KnowNowᵀᴹ Tests have been invented, developed and manufactured in the UK.
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.
The KnowNowᵀᴹ test will show a positive result from day 3 or 4 after exposure to the SARS-CoV-2 virus. This is earlier than other rapid antigen tests, which usually start to show positive results around day 5 or later.
This also means that individuals will receive a positive KnowNowᵀᴹ test 1 or 2 days before they are at very high risk of infecting others. So where there is a regular testing programme in place, individuals can quickly be isolated before they become highly infectious and the spread of the virus can be prevented.
The basis for this is our analysis of models of viral load in disease progression, such as the one shown within "Test sensitivity is secondary to frequency and turnaround time for COVID-19 screening" by Dr Michael Mina et al, alongside the low limit of detection of the KnowNowᵀᴹ test of 50,000 to 200,000 viral copies per mL.
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 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.
Used tests, swabs and buffer dropper tubes should be disposed of as potentially hazardous clinical waste.
At the moment, KnowNowᵀᴹ Tests are for professional use only, meaning that they need to be administered by a trained healthcare professional. This means that we can take orders from organisations that have in-house or outsourced healthcare professionals who can perform the tests, or testing service providers.
However, since the KnowNowᵀᴹ Test needs just a saliva sample, it is much easier to administer effectively than other similar tests, and still return highly sensitive results. So we are investigating whether specially-trained, competent individuals could be approved to administer KnowNow tests as well.
We are also in the process of trialling and seeking approval for a variation of the KnowNow test which could be administered by individuals themselves.