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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.

How does KnowNowᵀᴹ compare to COVID-19 antibody tests?

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.

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.

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.

When do you recommend tests are performed?

We recommend that tests are performed at the earliest opportunity possible, to ensure that individuals in the workplace, venue or community don't come into contact with each other prior to testing.

There's no particular time of day that's best to perform a test. Although it is important that individuals haven't had anything to eat or drink, and haven't smoked, within the 30 minutes prior to taking the test.

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 is SARS-CoV-2?

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.

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.

Where do you make your KnowNowᵀᴹ tests?

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

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

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