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Frequently Asked Questions

More Questions? Contact Us!
What is Cycle Threshold (Ct)?2021-02-09T14:06:15+00:00

The Ct or threshold cycle value is the number of amplification cycles a PCR test needs to perform on a sample before the fluorescence generated crosses the fluorescence threshold and is significantly above the background fluorescence.

At the threshold cycle, a detectable amount of amplicon product has been generated during the early exponential phase of the reaction.

The Ct is inversely proportional to the amount of RNA in the sample – if there is a low amount to start with it takes more cycles to amplify it enough to generate a signal.

If the sample has a high level of RNA (high viral load) it takes fewer cycles to generate a signal.

Is There Clinical Trial Data?2021-02-19T15:40:12+00:00


The Sichuan CDC where ran patient OP/NP swabs on RT-PCR (Da An Gene Co Ltd) and simultaneously on the AFS-1000 analyser with the SARS-C0V-2 cassette.

The clinical samples were across a wide range of Ct values and the study shows the Ct values for N and ORF1ab regions as well as the reading on the analyser for each test subject (the machine is designed to give a qualitative ‘positive/negative’ response but the results are semi-quantitative and can be downloaded).

In these clinical trials of 157 PCR-confirmed positives and 209 PCR-confirmed negatives, the AFS-1000 with the COVID-19 test cassette was 100% concordant with PCR positive results with Ct values ≤39. People are not infectious at Ct>34.

How Antibody Tests Work2021-05-23T15:50:21+01:00

Embedded into the test strip are antibodies that bind to a COVID-19 specific biomarker, the immunoglobulin specific to the viral spike (s) protein.

When a sample (blood, serum or plasma) is added to one end of the test, it flows along the test strip and interacts with these antibodies. If the test subject has had COVID-19 or a vaccine, the biomarkers in their blood will bind to the antibodies on in the test cassette and can be read by the AFS-1000 analyser.

Can Other Coronaviruses Affect the Test?2021-02-19T14:55:48+00:00

We’ve checked! No cross-reaction with human coronavirus HKU1 and NL63, influenza virus A H1N1 (2009), seasonal H1N1, H3N2, H5N1, H7N9, influenza B Yamagata, Victoria, Respiratory Syncytial Virus (RSV), rhinovirus A, B, C, adenovirus 1, 2, 3, 4, 5, 7, 55, enterovirus A, B, C, D, Epstein-Barr virus, measles virus, human cytomegalovirus, rotavirus, norovirus, mumps virus, varicella zoster virus or Mycoplasma pneumoniae.

AFS-1000: Technical2021-02-21T15:58:40+00:00

International Standards

Both the cassettes and the AFS-1000 reader are both CE marked as in vitro diagnostic medical devices under the IVDD 98/79/EC.

Regulatory approvals for Italy, Germany, Turkey, Colombia, Honduras, Dominican Republic. FDA EUA and authorisation by Health Canada under the Medical Devices Regulations are pending.

Cassette Storage and Stability

Keep in a cool, dry place. When stored between 2-30 ℃ the cassette remains valid for 18 months. Do not freeze.

Emission Frequency

The excitation frequency of the device is 475nm and the fluorescence emission from the region of interest of the LFIA test strip is 525nm.

Dimensions and Weight

The AFS-1000 are 300mm x 215mm x 150mm. Weight is 2.5 kg. Suitable for use in both point of care / need and laboratory settings.


Built-in printer supports automatic printing of test reports. Built-in 4G, USB2.0, RS232C, Wi-Fi, Ethernet, LIS, HIS. 7 inches 24 bits colour touch screen. 4D scanner.

Will the Antibody Test Show I’m Immune?2021-05-23T15:57:50+01:00

No. No antibody test can ‘prove’ immunity. Scientists are still unsure of the levels of immunity that result from getting the illness or getting a vaccine, the duration of any immunity and how robust it will be against future variants.

What Are Antigens?2021-02-09T14:06:15+00:00

An antigen is any substance that causes your immune system to produce antibodies against it. This happens when your immune system does not recognize the substance and is generating a specific response to it.

The nucleocapsid (N) protein of SARS-CoV-2 is an antigen, as is the S protein.

What is a Buffer Solution2021-05-23T15:54:36+01:00

A buffer solution acts as the carrier for the sample, allowing it to flow along the test strip. It also maintains a constant sample pH as it flows, preventing degradation of the reagents and the sample. Only use the buffer solution provided with the test kits as others may affect the accuracy of the test.

Also always use the buffer solution provided with each test batch. Do not mix buffer solutions between tests.

Are the Tests Accredited?2021-05-23T16:01:46+01:00

Yes. All our tests are CE marked for professional use and are therefore suitable and ready for use by healthcare professionals.

In addition to clinical evaluations already completed on the product, we are currently working with a number of independent laboratories and Departments of Health across Europe to further validate the product and gain best practice approvals.

What Is Immunofluorescence Assay?2021-02-09T14:06:15+00:00

Immunofluorescence is a technique used in many biological research applications.

Samples are mixed with a solution containing fluorescently labelled antibodies against the target (antigen) of interest – in this case the SARS-CoV-2 nucleoprotein.

These form antigen–antibody complexes if the n-protein is present.  These are captured in the test cassette and the immunocomplexes are detected by a fluorescence detector. The detector is very sensitive and can read signals invisible to the naked eye.

Immunofluorescence Test Limitations2021-02-21T15:48:26+00:00
  1. The SARS-CoV-2 Antigen Rapid Test Cassette is an acute-phase screening test for qualitative detection. Sample collected may contain antigen titles below the reagent’s sensitivity threshold, so a negative test result does not exclude infection with SARS-CoV-2.
  2. The SARS-CoV-2 Antigen Rapid Test Cassette detects viable and non-viable SARS-CoV-2 nucleoprotein. Test performance depends on nucleoprotein load in the sample and may not correlate with cell culture or other assays performed on the same sample.
  3. A positive test does not rule out the possibility that other pathogens may be present and does not rule out co-infections with other pathogens. Results must be compared with all other available clinical and laboratory information to make an accurate diagnosis.
  4. A negative test result may occur if the level of extracted antigen in a specimen is below the sensitivity of the test or if a poor-quality specimen is obtained.
  5. Performance of the test has not been established for monitoring antiviral treatment of SARS-CoV-2.
  6. Negative test results are not intended to rule in other coronavirus infections, only SARS-CoV-2.
  7. A negative result may occur if the concentration of nucleoprotein in a specimen is below the detection limit of the test or if the specimen was collected or transported improperly, therefore a negative test result does not eliminate the possibility of SARS-CoV-2 infection and should be confirmed by viral culture, NAAT molecular assay or ELISA.
  8. The accuracy of the test depends on the sample collection process. Improper sample collection, improper storage and repeated freezing and thawing of samples will affect the test results.
  9. The test results of this kit are only for clinicians’ reference and should not be used as the sole basis for clinical diagnosis and treatment. The clinical management of patients should be comprehensively considered in combination with their symptoms / signs, medical history, other laboratory tests and treatment reactions.
What Are Antibodies?2021-05-23T15:42:54+01:00

Antibodies are proteins produced by the immune system that bind to antigens to neutralise them or mark them for destruction by other wings of the immune system. The spike protein on SARS-CoV-2 is the protein antigen that allows the virus to attach to cells in our body to initiate an infection.

If our immune system has antibodies against the S antigen on the virus – resulting from exposure to SARS-CoV-2 or from vaccination –  they can bind to it and help prevent us from becoming infected. Other antibodies against SARS-CoV-2 have other roles, for example in recruiting other wings if the immine system.

With a SARS-CoV-2 infection, antibodies called IgM appear 7-10 days after infection and wane as the infection does.

IgG arrive after this but remain detectable longer—term; these alert the immune system to reinfection.

IgG against the S protein of the virus are a cornerstone of long-term immunity and there is a diagnostic cassette for the AFS-1000 to measure them in serum using a fingerprick blood test.

What Is Limit of Detection (LoD)?2021-02-09T14:19:27+00:00

LoD is the lowest detectable amount of the test target that a test can reliably distinguish from zero.

Low LoD is good = test needs LESS virus to be present in the sample for a positive result.

LoD impact on how much a COVID-19 test will tell us – some tests need more virus to be present than others to show a positive result.

Nucleic Acid Amplification Techniques (NAATs) such as PCR and LAMP can identify the virus in a sample that has a thousand viral RNA copies per millilitre (ml) or less. At those levels, test subjects will likely not be infectious yet.

For the sorts of visually-read lateral flow devices used in mass testing, that number is far greater and this is the principal reason they perform so poorly as a screening tool. Visually-read LFDs require the equivalent of hundreds of thousands to millions of copies per ml to show a positive result.

NAATs usually quote LoDs in copies per ml of sample. Other tests tend to use a different measure called TCID50 and comparisons between the two are difficult – but not impossible so comparisons between LoDs of the different tests can be estimated.

How Do False Positives and False Negatives Arise?2021-02-28T16:37:07+00:00

No matter how accurate a COVID-19 test is, there are statistical reasons a test result can be confusing, especially when what you’re testing for is rare. You might think COVID-19 is commonplace but probably less than 1% of the UK population has it at any one time.

ALL diagnostic tests have false positives and false negatives which need to be accounted for. But this creates some interesting statistical paradoxes.

False Negatives

Our test is 100% specific (its ability to correctly identify a positive) in people who are likely infectious – which is great because the level of false negatives (people who are infectious but not picked up by the test) will be very low.

In clinical trials, our test was proven to be 99.5% specific – which means it will correctly identify people who are definitely negative 99.5% of the time. Or, if you test 200 people who are definitely negative, statistically you may get one false positive. And if you test that person again, the probability is 1 in 200 x 200 – or 1 in 40,000 of an individual getting two false positives in a row.

False Positives

But what about false positives? People who are not infectious but test positive? There’s a fascinating statistical quirk here that was identified in 1763, but that affects all diagnostic tests, from COVID to all sorts of diseases, even workplace drug screening.

Let’s park COVID-19 testing for a moment and look at Bayes’ Theorem.

Say you have a test that is 95% sensitive (it picks up 95% of people who are definitely positive) and 95% specific (it picks up 95% of people who are definitely negative). Let’s also assume what you’re testing for is present in 1% of the population you are testing.

Let’s test 10,000 people

…and 1% have what you’re testing for

Should Test Negative
Should Test Positive

So that’s what we would expect were the test perfect. But it’s not. It’s 95% ‘accurate’. Which – because the incidence of what you are looking for is low – leads to some interesting statistical quirks. Let’s look at that again.


But here’s where it gets interesting. Because the low prevalence of whatever you’re testing for is low, the negatives get interesting.


Because 5% (95% specificity) of the 9,900 you expect to test negative is a bigger number than the true positives it can mislead you. Let’s do the maths:


It may surprise you that a 95% ‘accurate’ tests can deliver results where most of the positive results are false but it is a well known statistical anomaly, medics are well aware of it and take it into account when interpreting test results. The effect gets far smaller if specificity is closer to 100% or the prevalence of what the test is detecting is higher.

But the COVID-19 cassette used to diagnose is statistically 100% sensitive when used in people who may be infectious and clinical trials have shown it tracks PCR results 100% accurately to Ct values as high as 39.

COVID-19 Test Types2021-02-19T11:35:15+00:00

Since SARS-CoV-2 was first sequenced in January 2020 the testing market has burgeoned. Few people realise no mass tests look for the actual virus – each test looks for different components of the virus.

PCR was the first available test and is often referred to as the ‘gold standard’.  This is something of a misnomer as other assays now available are as accurate as PCR (‘accuracy’ is defined here). PCR has disadvantages. It’s expensive, needs a lab and highly-skilled technicians and time to result critical in terms of infection control it has a far greater impact on outcomes than incredible sensitivity figures.

Test Advantages Disadvantages
PCR Highly sensitive and specific, detects low levels of viral material so widely accepted by Governments for travel etc. Needs professional lab technicians to and a lab. Can still give a positive result long after infection has cleared. Very expensive. Takes 24-72hrs.
LAMP Point of care / need so can be used outside a lab. About an hour. Needs professional lab technicians to operate. Can still give a positive result long after infection has cleared. Quite expensive.
LATERAL FLOW ANTIGEN Cheap – £5-10 per test, no specialist staff required. Rapid – 15-30mins Only identifies people with the highest viral loads so a negative result does not guarantee you are not infected or not infectious.

NB Antibody testing only picks up previous infections, not current ones.

If we summarise the choices, until now the options have been:

  • PCR which is highly accurate but takes time to process and is expensive;

  • LAMP which can be used point of care but is technically more demanding than people had thought;

  • LFDs which are simple, cheap and rapid – but lack diagnostic power.

Current LFDs have been promoted by government as suitable for identifying the infectious and do have their uses – as a rapid aid in clinical diagnosis of a symptomatic patient, or in public health screening and large-scale public testing. But in trials they identified as few as 30% of the people who tested positive on PCR.

The AFS-1000 COVID-19 Cassette can pick up a current infection with accuracy on a par with PCR and LAMP in 15 minutes. 

How Accurate is the Test?2021-02-19T12:54:26+00:00

There are actually three ways the accuracy of diagnostic tests is measured. How likely are they (%) to diagnose someone who has the infection (sensitivity), how likely are they (%) to correctly diagnose someone who doesn’t have the infection (specificity) and how much of the virus needs to be in a sample for a test to reliably pick it up.

For this test, clinical trials included 157 clinically sourced positive and 209 confirmed negative NP / OP samples. The positive coincidence rate (sensitivity) was 96.2% and the negative coincidence rate (specificity) was 99.5%. This gives a Positive Predictive Value (PPV) of 99.3%, and a Negative Predictive Value (NPV) of 97.1%.

The limit of detection was calculated using a reference solution of inactivated virus supplied by the Wuhan Institute of Virology, Chinese Academy of Sciences, with an original concentration of 1×104 TCID50/ml. This was used to calculate the limit of detection as 0.02ng/ml (recombinant N protein), or 0.5TCID50/ml (inactivated virus). Using latex agglutination immunochromatography method the calculation is 0.1ng/ml (recombinant N protein), or 1TCID50/ml (inactivated virus).

The MHRA Target Product Profile asks for LoD in RNA copies per ml and by using a number of coefficients to convert from both TCID50 and ng/ml we estimate it to be under 1,000 copies per ml of sample.

For comparison, lateral flow tests generally need 100-300 TCID50/ml present to reliably show a positive – so this test needs 200x – 600x less viral material in a sample to correctly identify a positive. 

What Other Tests Are Available?2021-02-20T21:36:00+00:00

Multiple diagnostic tests can be run on the AFS-1000 including for cardiac issues, infectious disease, and sepsis. This versatility can be very useful in primary care, remote locations and triage.

Tests include:

Test Description Sample
BNP Type B natriuretic peptide Serological
CTNL / MYO / CKMB Triple detection of myocardium Serological
BETA-HCG Beta human chorionic gonadotropin Serological
CRP C-reactive protein Serological
CTNL Cardiac troponin Serological
D-DIMER D-Dimer Serological
HBA1C Haemoglobin A1C Serological
HS-CTNL High sensitivity cTnl Serological
IL6 Interleukin- 6 Serological
NT-PROBNP N terminal pro B type natriuretic peptide Serological
PCT Procalcitonin Serological
SAA Serum Amyloid A Serological
How Does This Test Work?2021-03-02T17:08:36+00:00

In simple terms the test cassette contains specially-engineered proteins (antibodies) that attach to the SARS-CoV-2 nucleoprotein (if it’s present in the sample) and these antibodies have a light-emitting chemical bonded to them that is read by the AFS-1000.

The more technical version is the reagent the swab goes into breaks the virus apart so the test can get at the part of the virus it’s looking for (the nucleoprotein).

After treatment with the reagent in the dripper, the sample is added to the sample well in the cassette. If the virus is present, its nucleoprotein and a labelled antibody in the cassette (monoclonal antibody against SARS-CoV-2 nucleoprotein) form an immune complex. This complex moves with the liquid along the nitrocellulose membrane in the cassette.

Further along the cassette there are other antibodies bound to the membrane. These attach to the n-protein / immunofluorescent antibody complexes thereby trapping them – but they do NOT trap any unbound antigen.

When the sample contains SARS-CoV-2 antigen it (along with the fluorescent marker that has bound to it) concentrates in the detection area of the cassette – and the AFS-1000 can read if the signal there is higher than the background. If it is the test is positive, if not it’s negative.

The reagent consists of test card, ID chip card, sample preservation solution (optional), dripper and swab. The test cassette consists of reagent strip and plastic case. The main components of the test strip are fluorescence labelled SARS-CoV-2 nucleoprotein monoclonal antibody and another nucleoprotein monoclonal antibody adsorbed to the detection area of the nitrocellulose membrane.

Anti-mouse immunoglobulin G polyclonal antibody is fixed in the quality control area of the nitrocellulose membrane. This proves that the cassette is working properly and ensures a faulty cassette cannot be misinterpreted as a negative test.

The main preservation solution is phosphate buffer (PBS, 50mM, ph7.2).

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A game-changing innovation in COVID-19 testing.

A game-changing innovation in COVID-19 testing.

Only diagnoses active infections – no false positives from past infections unlike PCR and LAMP

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