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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.

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.

What does a positive test result look like and mean?

Positive KnowNowᵀᴹ Test result
Positive KnowNowᵀᴹ Test Result

If there is one red line visible next to the "C" in the KnowNowᵀᴹ device test results window, and any line at all, no matter how faint, appears next to the "T", then the test result is positive. This indicates that the SARS-CoV-2 antigen has been detected in the sample.

Following a positive result, current government guidance on matters including self-isolation and reporting the result should be followed.

How does KnowNowᵀᴹ compare to other COVID-19 lateral flow antigen tests?

The KnowNowᵀᴹ Test is unique to other lateral flow antigen tests in 3 key areas.

The first key difference is that the KnowNow test needs only a saliva sample, which can be taken easily and comfortably from the mouth. Other lateral flow antigen 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 is that the KnowNowᵀᴹ Test looks specifically for live virus which would cause the individual tested to be able to infect others. Although other lateral flow antigen tests are often said to test whether an individual is infectious, this is because they have a higher Limit of Detection and can only detect the virus when there are more viral particles present in the sample. As a result, they offer a proxy measure for infectivity, rather than directly testing whether there is live virus in the sample. The KnowNowᵀᴹ Test on the other hand is a true infectiousness test, which uses a unique patented mechanism which detects a completely different part of the virus.

Finally, the KnowNowᵀᴹ Test is also more sensitive than other rapid antigen tests available, as it is able to pick up the presence of the virus even when there is much less of it present in the sample. Our Limit of Detection is between 50,000 and 200,000 viral copies per mL, whilst the Abbott BinaxNow test, for example, needs 1,000,000 viral copies per mL in order to get a positive signal.

Isn't lateral flow testing less good than PCR testing?

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.

How sensitive is the KnowNowᵀᴹ Test?

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 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 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 Limit of Detection values for tests using universal standard metrics should be readily available in the public domain to enable like-for-like comparison.

Is it necessary to perform multiple tests to be sure of the result?

It should not be necessary to perform more than one test on a given individual at a single point in time, unless the KnowNowᵀᴹ device test results window displays no lines at all, meaning that the test has failed, or unless it was not possible to read the test results within 15 to 60 minutes of applying the mixed saliva and buffer solution to the KnowNowᵀᴹ device.

However, receiving a negative result does not mean that the individual tested can't be exposed to the SARS-CoV-2 virus following the test. So we do recommend that individuals are tested regularly to keep workplaces and communities safe. Depending on the scenario, we would recommend testing is repeated every 1 to 3 days.

How soon after exposure would the KnowNowᵀᴹ Test give a positive result?

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.

Does the KnowNow Test identify all COVID-19 mutations?

The mechanism underpinning the KnowNowᵀᴹ test mimics the means through which the virus interacts with the surface of a human cell in order to detect it. As a result, we expect that it will continue to identify the SARS-CoV-2 virus even in the face of further potential mutation in the future, unlike tests based on antibodies.

We have modelled the difference between the Wuhan and 501Y mutations in a recombinant protein model to give us initial analytical evidence that the KnowNow test reacts to these variations of concern. And we are currently carrying out a study on live samples of these and other mutations to gather practical evidence of this.

In fact, we predict that the KnowNowᵀᴹ test may potentially become even more sensitive as the virus mutates to become more infectious. And we will continue to carry out further analyses and studies to support this prediction, and confirm that KnowNow continues to function on newer mutations as they arise.

Is KnowNowᵀᴹ approved and safe?

The KnowNowᵀᴹ test has been developed to Vatic's stringent standards of quality and safety.

It has undergone the necessary clinical trials and performance tests and has been shown to meet the specific requirements published by the UK's Medicines and Healthcare Products Regulatory Agency (MHRA).

The KnowNow test has been CE marked for professional use in a healthcare setting and has been registered for use in the UK and the EU.

How should KnowNowᵀᴹ tests be stored?

KnowNowᵀᴹ Tests should be stored between 2 and 30 degrees celsius, which means it's fine to store it at room temperature in the UK's mild climate.

There's no need to store it inside a fridge, unless you're expecting extremely hot weather. If you do choose to refrigerate the test though, just make sure it comes to room temperature before using it.

The KnowNowᵀᴹ Test device should also be stored still sealed in its foil pouch. Once removed from the foil pouch, it should be used within one hour.

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