FAQ - How to test for the presence of Coronavirus (Covid-19) on surfaces with COV-HYGIEN XPRESS

  • Product-related questions
  • Application-related questions

What documentation is available for the product?

In the Documentation section of this website you will find the product flyer, detailed Instructions For Use (IFU), and a Data Sheet with information on the product's limit of detection (LOD) and specificity, all of which are available for download.

We are making an effort to provide relevant information in multiple languages.

The IFU are currently available in English, French, and Spanish, and will soon be available in Italian, German, and Portuguese.

You can find these documents in the Documentation section.

The Material Safety Data Sheets and Certificates of Quality are available upon request; use the Contact form or contact us directly at contact@biomire.solutions

What is the difference between the detection kit and the surface kit?

We refer to the step involving the test strip as "detection".

The initial protocol steps, which involve preparing the swab and using it to sample surfaces, can be referred to as the "pre-analytic" steps.

The surface test involves both the pre-analytic steps and detection.

The COV-Hygien Xpress kit for Surfaces contains all of the components necessary to perform a surface test, including the swabs.

The COV-Hygien Xpress Detection kit is identical to the COV-Hygien Xpress kit for Surfaces, except that it does not include any swabs.

The detection kit is designed for users who may wish to:

- use their own swabs, which they are already familiar with

- test liquid samples

- test particles that have been collected on a surface from air samples, e.g. using the Compact Coriolis cyclonic sampler

What is the smallest number of coronaviruses that the kit can detect ?  

During the development phase, the analytical performance of the detection strips was tested using a 2-fold serial dilution of the virus (in viral culture medium) in parallel with titration of the same viral preparation in Vero E6 cells (by plaque assay).

Materials and methods

SARS-CoV-2 passage 3 (SARS-CoV-2-Iso_01-Human-2020-02-07-Swe, accession no./GenBank no. MT093571) was cultured in Vero E6 cells. The titer was determined by plaque assay, with cells fixed 72 hpi. All experiments involving SARS-CoV-2 were performed in the Biosafety Level 3 Laboratory at the Public Health Agency of Sweden (Folkhälsomyndigheten, Stockholm, Sweden).


The detection strip was shown to be able to detect virus at concentrations as low as 5,000 pfu/mL (pfu: plaque-forming units).

Note that these results may vary with viral preparation method, cell line infected, culture media composition and in particular the presence of serum, as well as with lysis conditions.

The swabbing step has a significant impact on the LOD because it determines the % of virus that is lifted off the surface, the % of virus lifted onto the swab that is resuspended in the liquid reagent, and the dilution of the virus in the resuspension buffer.

Even supposing that the % of virus lifted onto the swab and resuspended in the buffer are identical for (i) a sample tested on site with COV-Hygien Xpress and (ii) a sample sent to a laboratory for PCR testing, the viral dilutions are typically different. This is because the virus is typically resuspended in 3 mL of transport media for PCR analysis,whereas the volume of resuspension buffer recommended for the COV-Hygien Xpress kit is 0.45 mL.

In theory the LOD on surfaces is expected to be the same for both methods. We are currently carrying out tests to confirm this theory.

If you would like to conduct a study that involves detecting SARS-CoV-2 on surfaces, please contact us: we would be happy to facilitate your work!

Is the product for detection of coronavirus on surfaces only? 

The COV-Hygien Xpress  Detection kit can be used for the detection of coronavirus from samples other than surfaces.

The COV-Hygien Xpress Detection kit is identical to the COV-Hygien Xpress kit for Surfaces, except that it does not include swabs.

The detection kit is designed for users who may wish to:

- use their own swabs, which they are already familiar with

- test liquid samples

- test particles that have been collected on a surface from air samples, e.g., using the Compact Coriolis cyclonic sampler

For these applications, 100 uL of the sample should be mixed with 100 uL of COV-Hygien Xpress buffer prior to detection

Where is the kit manufactured?

The kit includes components from different sources.

The essential reagents are manufactured in Europe in an ISO 13485–certified environment. 

Other important components such as the swabs are obtained from Europe and the USA

Additional components such as the labels, tube holders, and markers are obtained from France but may have been manufactured elsewhere.

The kits are assembled in an ISO 9001– and ISO 14000–certified environment.

Why does the control line sometimes appear very faint compared to the positive test line?

The purpose of the control line is to indicate that the sample has migrated properly to the top of the strip. It is not related to the test result itself.

The control line may appear slightly faint compared to a positive test line because the positive test line has "trapped" some of the color conjugate, so less of the color is available to reach the control line. (See "How does the test work?")

In these cases, the faintness of the control line has no effect on the test result, which should be considered positive.

What if the test "runs" longer than the recommended time?

Running the test for up to 30 minutes instead of 15 minutes does not significantly affect the results, and may marginally improve the detection of a positive result.

We do not recommend allowing that test to run for longer than 30 minutes, as this may lead to the appearance of a false positive signal.

What is the kit's shelf life, and how stable are the components after opening?

Before opening

The kit's shelf life (printed on the box label) is limited by the kit component with the shortest shelf life.

Currently, this is the Immuno-Detection strips, which have been demonstrated to have a shelf life of 12 months (printed on the strip pouches).

Shelf life is determined by real-time aging studies, which are currently underway to confirm whether this limit can be extended.

Typically, Immuno-Detection strips have a shelf life of 18 to 24 months, and we expect the COV-Hygien Xpress kits to show similar stability.

After opening

The kit reagents (buffer and strips) are stable for at least 15 weeks after first opening, if properly stored.

Stability depends on the storage conditions.

- The recommended storage temperature is between 4°C and 30°C (39°F to 86°F)

- Immunochromatographic tests uses nitrocellulose supports, which are sensitive to humidity. Each strip pouch contains a desiccant. We recommend promptly closing and sealing pouches after removing a strip, for example by folding the pouch edge and/or applying sealer tape. 

A test strip used 15 or 20 weeks after the pouch has been opened can be considered valid if the control line appears.

What are the minimum and maximum sample volumes that the tube can accommodate?

The minimum sample volume needed to run a test is 150 uL.

The maximum volume is dictated by the level of liquid in the tube.

The line immediately under the two red arrows indicates the upper limit for the sample.

While handling the tube containing the sample and the strip, care should be taken not to wet the strip above this line. It is important that any moisture above this line reach this portion of the strip through capillary action only.

If the sample limit line is exceeded accidentally because a tube other than the one provided is used, the test may still be considered valid as long the sample does not reach any higher than the arrow heads (a couple of millimeters above the the upper limit line).

What are the storage conditions for the kit?

The reagents should be stored at between 4°C and 30°C.

Close all pouches immediately after removing a component, and close the dropper vial immediately after use.

 Do you sell smaller versions of the kit (5 tests/pack)?

No, currently we only offer a kit containing 25 tests.

You can very easily divide the 25-test kit into smaller packs of five tests each, as most of the components are packaged in units of five each.

The components are packaged this way for two reasons:

- for convenience, so that multiple users can test different sites at the same time

- to avoid waste: the critical reagents (strips and buffer) should be used within 3 weeks after opening, whereas their shelf life when unopened is several months; packaging the components in units of five helps avoid waste

Is there a discount for buying kits in large quantities ?

A discount is automatically applied when you order 10 boxes from our store.

For larger orders, larger discounts are available. Please contact us for more information.

Do you offer free samples for customers or for demonstration purposes?

We do not provide free samples of individual tests because of the way in which the kit components are packaged.

We can supply the kit in a customized smaller size (5 tests/pack) for trials. Please contact us to discuss your needs and shipping fees.

We are happy to facilitate environmental or validation studies in any way we can, including offering significant discounts, provided that you share your results with us. If you are interested in discussing this further, please contact us.

How are the kits shipped? 

Our default carrier is DHL.

To arrange for your preferred carrier to pick your order up at our logistics center, please contact us.

How does Immuno-Detection work for viruses?

Lateral flow tests, also known as lateral flow immunochromatographic assays, detect the presence of a target substance in a liquid sample without the need for specialized and costly equipment.

Immuno-Detection refers to the fact that this technique involves the interaction between an antibody and an antigen, one of which is the target. In a serological test for COVID, the target is the antibody present in the patient's blood, and the test kit contains the antigen.
In the case of COV-Hygien Xpress, a viral protein is the target, and the test kit contains the antibody.

These tests are widely used in medical diagnostics for home testing, point-of-care testing, or laboratory use.

In essence, the test strip is a series of absorbent materials that have the capacity to transport fluids spontaneously, by capillary action. Several of these materials contain specific reagents, either in a free form, in which case they will be carried along by the flow of liquid, or immobilized, in which case they stay were they are. 

When a test is run, a sample is added to the sample pad. The sample first migrates through the conjugate pad, which contains the first antiviral antibody conjugated to a colored particle (hence the name conjugate).
The conjugate is carried along by the sample flow, attaches to the virus if it is present, and continues to flow across the test and control lines.

When the sample hits the test line, a second immobilized antiviral antibody catches the virus and the attached conjugate. As more and more viral particles become trapped at the test line, the local concentration of the conjugate increases, and the color becomes visible.

Any hint of color, even faint color, observed at the test line indicates that some virus is present, and should be considered a positive result.

The conjugate is present in excess of the amount of virus that is potentially present in the sample, so some of the conjugate continues to flow upward to the control line.

An anti-antibody is immobilized on the control line and catches the conjugate antibody. (Anti-antibodies are antibodies from one species, e.g. goat, that react to antibodies from another species, e.g. rabbit.) As the conjugate accumulates at the control line, the color of the line intensifies.

The purpose of the control line is to confirm that the test worked, even if no color change was observed at the test line.

What does the COV-Hygien Xpress kit detect ?

The test detects the SARS-CoV-2 Nucleocapsid Protein (NP).

Nucleocapsid protein (NP) is the most abundant protein on the helical nucleocapsid of coronaviruses, which envelopes the entire genomic RNA. NP also interacts with other viron structural proteins to play important roles during host cell entry and virus particle assembly and release. Anti-NP antibodies have been shown to be the earliest and the most predominant antibodies detectable in patient’s blood samples after coronavirus infection.

The effectiveness of sanitization is routinely monitored by assessing the quantity of microorganisms present, either using culture methods, which are quantitative and very informative but slow, or by measuring ATP, which is qualitative and less informative but rapid.

Tests used to quantify viable viruses, such as plaque assays, are long, complicated, and expensive to perform. They involve infecting slow-growing, fragile mammalian cells. This type of technique is inappropriate for hygiene monitoring. 

Techniques that detect viral markers such as viral genes (by PCR: polymerase chain reaction) or specific viral proteins (by Immuno-Detection) are faster and less expensive and are sufficiently presumptive of viral presence to be valuable for hygiene monitoring.

How can I compare PCR and Immuno-Detection for monitoring surfaces for coronavirus contamination?

When comparing methods for monitoring the presence of viruses on surfaces, the entire test should be considered, i.e. swabbing of a surface and detection of the resuspension.

Because PCR (which targets viral RNA) and Immuno-Detection (which targets a viral protein) do not detect the same target, these technique should be compared using samples containing intact virus.

Hygiene monitoring tests such as COV-Hygien Xpress are designed for use on site, but intact virus is hazardous and must be handled in an appropriately equipped laboratory, which explains the current lack of true comparative data. 

Studies to determine the limit of detection (LOD) on common surfaces are in progress and will be shared soon.


The swabbing step has a significant impact on the LOD because it determines the % of virus that is lifted off of the surface, the % of virus lifted onto the swab that is resuspended in the reagent, and the dilution of the virus in the resuspension buffer.

Even supposing that the % of virus lifted onto the swab and resuspended in the buffer are identical for (i) a sample tested on site with COV-Hygien Xpress and (ii) a sample sent to a laboratory for PCR testing, the viral dilutions are typically different. For PCR analysis the virus is typically resuspended in 3 mL of transport media, whereas the volume of resuspension buffer recommended for COV-Hygien Xpress is 0.45 mL.

Thus, when the complete test protocol is carried out, the virus is diluted less by the standard COV-Hygien Xpress protocol than by a standard PCR protocol.


The following two studies compared PCR to Imumuno-Detection (the technology behind COV-Hygien Xpress) in a clinical context. The comparisons were made using clinical samples to determine whether Immuno-Detection is suitable for diagnostic use in humans, and only evaluated the detection methods.

Front. Med., 08 May 2020

- Journal of Clinical Microbiology Jun 2020, JCM.00977-20; DOI: 10.1128/JCM.00977-20

The data show that Immuno-Detection has high sensitivity, although it was not quite as sensitive as PCR in clinical samples, and that both techniques are equally specific.


Overall, both methods can be expected to have similar LODs.

Can I use my usual ATP Hygiene monitoring tests to detect coronavirus?

ATP-based tests are widely and successfully used for hygiene monitoring, but cannot be used to detect viruses, as viruses do not contain ATP.

Can COV-Hygien Xpress detect SARS-CoV-2 that has been on a surface for several hours?

The test is less likely to detect the presence of virus on a surface after several hours, as the virus is relatively fragile.

The COV-Hygien Xpress test detects a specific and abundant SARS-CoV-2 protein. 

If this protein is damaged, the test will be less able to detect it.

If the protein is damaged, this indicates that the virus is also damaged, but the virus can be damaged in other ways than by damaging the protein.

Detection of the virus on a surface by COV-Hygien Xpress does not mean that the virus is infectious, simply that it was present.

SARS-CoV-2 is an enveloped RNA virus that is not very robust: 

  • If the protein targeted by the test is sufficiently damaged, the test will be less able to detect it
  • If the protein is damaged, this indicates that the virus is also damaged

After sanitization, the protein should not be present. If the virus is detected by hygiene monitoring, the cleaning procedure was not effective and should be carried out again or improved.

Viral survival on surfaces

Multiple studies have determined how long the virus can survive on various types of surfaces:

  • Metal: doorknobs, jewelry, silverware, etc. - 5 days
  • Wood: furniture, decking, etc. - 4 days
  • Plastic: milk containers, detergent bottles, subway and bus seats, backpacks, elevator buttons, etc. - 2 to 3 days
  • Stainless steel: refrigerators, pots and pans, sinks, some water bottles, etc. - 2 to 3 days
  • Cardboard: shipping boxes, etc. - 24 hours
  • Copper: pennies, teakettles, cookware, etc. - 4 hours
  • Aluminum: soda cans, tinfoil, water bottles, etc. - 2 to 8 hours  
  • Glass: drinking glasses, measuring cups, mirrors, windows, etc. - up to 5 days
  • Ceramic: dishes, pottery, mugs, etc. - 5 days
  • Paper: mail, newspaper, etc. - only a few minutes, although some coronavirus strains survive on paper for up to 5 days

The effect of sanitizing agents on coronavirus

Why is it important to monitor disinfection efficacy ?

It is important to monitor the efficacy of cleaning and disinfection for SARS-CoV-2, as slight changes in disinfectant concentration or contact time can have significant unintended consequences

Monitoring confirms that no detectable quantities of virus are present. 

A positive result after sanitization indicates that the surface should be sanitized again.

The activity of disinfectant products is dependent on their concentration, pH, and temperature, as well as the presence of biological products (blood, secretions, etc.), the ability of viruses to aggregate, and more.

If an area has been disinfected prior to testing, will this affect the test?

Yes, potentially, as for most biological assays.

The control line and test line antibodies, as well as the conjugate, all contain proteins that play an active role in the detection of the viral protein.

(See FAQ "How does Immuno-Detection work for viruses?")

Damage to the viral protein may render it undetectable. In this case, the virus is inactivated, so the test result will be negative, which is consistent with the absence of (functional) virus.

As for any test that involves proteins (the vast majority of tests), damage to any of the proteins in the kit reagents can compromise the test. Antibodies are resistant to degradation, particularly when immobilized on a surface, and a sample would need to contain exceptionally high concentrations of specific compounds for the test to be compromised; formaldehyde is an example.

To prevent the interference of cleaning agents in hygiene monitoring for bacteria or otherwise, recently sanitized surfaces should be allowed to dry before swabbing. This allows the sanitizing agent to evaporate, thereby limiting its potential to interfere with the test.


Need help setting monitoring thresholds, interpreting microbial counts and adjusting your sanitization procedures, mapping your facility, designing a monitoring plan, or anything else?