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Why does the KnowNowᵀᴹ test use a saliva sample?

We chose to design our unique KnowNowᵀᴹ test for COVID-19 infectiousness to work with a simple saliva sample, so that it would be comfortable and easy to administer, and to ensure that anyone would be happy to take a test every day if required. We believe that patient comfort and happiness leads to increased participation in routine testing, and ultimately increases the probability that COVID positive patients can be detected before they've had a chance to infect others.

The focus of our first clinical study was to assess the feasibility of using saliva sampling, to refine our saliva collection method, and also to assess the overall usability of the KnowNow test. This was a UK Government-supported National Institute for Health Research (NIHR) study carried out across ten UK hospitals with 100 patients participating. Through this study we determined that saliva sampling was both effective and user-friendly, and identified a specific swab for sampling. We chose not to opt for a spit collection method for our saliva sample, as providing a spit sample can be challenging for some patients, particularly the elderly or those suffering with COVID-19 symptoms.

For other COVID-19 tests, throat and nasopharyngeal swabbing is one of the most common types of sample collection. However, a number of studies have explored various issues with these types of sample collection, including:

  • The sample collection method requires a swab to be inserted into the patient's throat and/or far into their nostril and rotated, causing discomfort to patients due to the procedure’s invasiveness, and even inducing bleeding in their tonsils and posterior pharynx. (1)
  • The discomfort or even pain of the sample collection method has a detrimental impact on compliance for serial testing, as patients are unwilling to subject themselves to the test on a regular basis. (2)
  • Nasopharyngeal sample collection presents a considerable risk to healthcare workers, because it can induce patients to sneeze or cough, expelling virus particles. (2)
  • There are several situations where nasopharyngeal swabs would cause particular harm, such as in patients with coagulopathy, those undergoing anticoagulant therapy, or those with significant nasal septum deviation. (3)
  • These tests are not always successful at the first attempt, even though performed by trained healthcare workers, and shortages of swabs and protective equipment are frequently reported. (3)
  • They show relatively poor sensitivity for SARS-CoV-2 detection in early infection and are inconsistent during serial testing. (2)

Some tests have been designed to work with anterior nasal swabs, as a somewhat less invasive alternative to nasopharyngeal swabs. However, there is some evidence to suggest that nasal swab testing produces less sensitive results and may miss patients with lower viral loads (4).

References:

(1) Exploring salivary diagnostics in COVID-19: a scoping review and research suggestions

(2) Saliva is more sensitive for SARS-CoV-2 detection in COVID-19 patients than nasopharyngeal swabs

(3) Saliva as a Candidate for COVID-19 Diagnostic Testing: A Meta-Analysis

(4) Nasal-Swab Testing Misses Patients with Low SARS-CoV-2 Viral Loads

How does KnowNowᵀᴹ compare to COVID-19 PCR tests?

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.

How much space do I need to store the tests?

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.

Why test people who don't have symptoms?

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.

Where do you make your KnowNowᵀᴹ tests?

KnowNowᵀᴹ Tests have been invented, developed and manufactured in the UK.

What does a negative test result look like and mean?

Negative KnowNowᵀᴹ Test Result

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.

How accurate are your tests?

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.

What is a lateral flow test?

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.

Is it possible to tell if the test has been carried out incorrectly?

Failed KnowNowᵀᴹ Test Result
Failed KnowNowᵀᴹ Test Result

Yes, it will be very clear if the test has been carried out incorrectly and failed.

If there are no lines at all visible in the KnowNowᵀᴹ device test results window, then the test has failed, and it should be repeated with a new device and a fresh saliva sample.

Can anyone order KnowNowᵀᴹ Tests?

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.

Do you identify infection in people who are asymptomatic?

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.

Had COVID - 19 symptoms in the last 2 days? Apply here to help us make testing accessible to all.