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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.

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.

Are there any health risks to or side effects from taking the KnowNowᵀᴹ Test?ᵀ

There are no health risks associated with using the KnowNow test itself, and it is safe to use on all individuals.

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 this regular testing is combined with mask wearing, hand washing and social distancing, the risk of virus transmission is vastly decreased.

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.

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 specific is the KnowNowᵀᴹ Test?

The KnowNowᵀᴹ Test's specificity is 100%. In more than 700 negative patient saliva samples, it hasn’t returned a single false positive result.

This is so important for getting life back to normal. We don't want anyone to be stopped from going to work, heading off on holiday or socialising at events, when actually it would be perfectly safe for them to do these things.

Specificity is particularly important when disease prevalence is low and tests are intended to be used at enormous scale. For example, if a test with just a 3% false positive rate is used on one million people per day, that would result in 30,000 people per day being falsely identified as infectious with COVID-19 and being unnecessarily asked to self-isolate.

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.

I've already activated my sample pack

If you have already activated your sample pack please go to the activation link that we emailed to you. Alternatively, if you fill in your email again we will re-send the activation link to you.

Where do you make your KnowNowᵀᴹ tests?

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

How long does a negative test result last for?

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.

What is a KnowNowᵀᴹ Test?

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.

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