Pluslife FAQ (EN)

This website is a non-commercial knowledge base for researchers and nerds. It is not intended for the general public and makes no claim to completeness, accuracy or being up-to-date. It can in no way replace a consultation with qualified medical personnel.

Pluslife is a commercial, molecular LAMP assay for the detection of SARS-CoV-2 RNA. It is similar to (but much cheaper than) devices like Lucira or Cue, which are only available on the US market.

Costs are about ~5-7€ per test and 150-300€ for the device itself. It is the only affordable molecular Covid test procedure currently available in Germany.

The tests are very simple to use, but require careful work and some attention to detail. Use them outside the professional environment at your own risk.

To perform the test correctly, it is sufficient to work exactly according to the instructions supplied by Pluslife. We recommend wearing protective gloves. This website is intended to provide extra background information, you don't have to read it to use the tests successfully.

Sensitivity

The manufacturer specifies a 95% LOD ("Limit of Detection") of 400 copies/mL. The LOD is the lower limit of sensitivity: a sample containing 400 viral RNA copies per mL was correctly detected as positive in 19 of 20 samples when tested by the manufacturer.

This is an excellent result and is within the range of lab PCR tests, which typically have LODs between 50 and 1000 copies/mL, depending on the quality of the PCR assay.

We have been able to independently validate the manufacturer's claims.

For comparison: a rapid antigen test requires millions to tens of millions of RNA copies/mL, multiple orders of magnitude worse! Here is an attempt to represent these huge quantities as cube volumes:

In contrast to conventional rapid tests, which rely on direct detection of the pathogen, Pluslife tests enable early detection of an infection through exponential amplification of genetic material, usually before viral load is high enough for transmission.

Molecular tests such as Pluslife offer a high degree of certainty and can enable social interactions that would otherwise be too risky.

How to buy

Device and tests are sold by Altruan. For non-commercial use, Altruan worked with us to offer special conditions to our community - email us for details (discount [ät] virus.sucks).

Altruan is the only importer in Germany, everyone else buys from them.

This website is private, independent and non-commercial. We do not receive any commission or other compensation.

Tips and tricks

Avoid DNA contamination

The LAMP method, on which the Pluslife tests are based, is based on the exponential amplification of target gene sequences. The viral RNA is first converted to DNA (reverse transcription) and the target sequences - if present - are then amplified using a polymerase enzyme. A few RNA copies become billions of DNA copies, which can be easily detected using an optical method.

However, this also means that the test cards contain very high quantities of these DNA snippets ("amplicons") after the test. Although these are harmless to humans and the environment and are in no way infectious, they can contaminate the environment if handled incorrectly.

The procedure is very sensitive and even the smallest quantities that escape are sufficient to contaminate subsequent reactions or even people, which then leads to false positive results. Pluslife tests would therefore be useless in contaminated rooms or for contaminated persons who spend longer periods of time in contaminated rooms.

DNA is very robust, cannot be removed with most disinfectants and degrades very slowly (unlike viral RNA). It can remain detectable in indoor air and dust for years. Contamination should therefore be avoided at all costs.

Never open the test card after the reaction and remove cards from the device immediately after testing. Dispose of them in the bags provided.

Handle positive tests with particular care, always remove the test cards with protective gloves and then change the protective gloves.

If the test card does leak after a positive result, false positive results must be expected in the future. If possible, dispose of or decontaminate all objects that have come into contact with the liquid using disposable gloves.

Detect contamination

If contamination is suspected, the environment and the test device can be swabbed with a damp swab and then tested normally without a human sample. If this control is positive, although no one in the environment is ill, there may be contamination.

DNA contamination is very rare and we are not aware of any cases outside of laboratories. If you suspect contamination due to a positive environmental control, we will be happy to help you with decontamination - please contact us by email.

False positive results

Pluslife tests are very specific. Unlike other LAMP assays such as Lucira, false positive results are very rare. All cases known to us were due to air bubbles rather than unspecific amplification.

Air bubbles can move within the test card due to the heat. Condensation can form within the air bubble, which can cause a sudden increase in the optical signal, which the device then incorrectly evaluates as a positive result.

With our app such an abrupt increase is easy to recognize.

If false positive results are suspected, the test should be repeated completely, including taking a new sample and, if possible, using a different batch of the test kit. If the result is negative on retesting, it is a false positive result. If the result is positive again, a positive result should be assumed.

Invalid results

In addition to the actual Covid target genes, the test cards also contain an internal control that tests for a gene sequence present in each sample and is therefore always positive. It tests for the presence of the human housekeeping gene β-Actin.

If the internal control fails to amplify or the signal isn't strong enough, the result will be invalid.

The test card contains several test chambers and a reaction takes place in each chamber. If any of them become positive, the test is positive.

By far the most common causes are air bubbles or waiting too long after inserting the card as well as contaminated samples (blood, food, too much nasal secretion..). Possible sources of error also include expired test kits or oversized pools.

Storage of the test kits

The test kits should be stored in a cool and dry place between 2°–28° C.

The manufacturer has stated that the test kits have remained stable in experiments between -20–55 °C, so temperature fluctuations during transportation are harmless.

Frequently asked questions

How long is the test result valid?

We are not aware of any studies that could conclusively answer the question. It is a question of individual risk assessment and pre-test probability (overall risk).

Many experts consider a period of approx. 12 to 24 hours to be safe and appropriate.

A negative Pluslife test is a very strong indication that the person was not infectious at the time of the test. Within the incubation period since the last higher-risk contact, this can of course change and the test must be repeated regularly within the possible incubation period.

If the risk is very high, it makes sense to repeat the tests more frequently than if the risk is low.

The more sensitive a test, the earlier it can detect the virus at the start of the exponential growth phase when viral loads are still very low. This implies a greater "safety buffer" than less sensitive tests: the period during which the virus can already be detected but the person is not yet infectious. While this safety buffer is essentially zero with normal rapid tests, a molecular test such as Pluslife offers a certain degree of safety.

Will throat swabs also work?

Yes. The manufacturer has confirmed that both nasal and throat swabs have been validated. The reason the package insert does not mention throat swabs is due to the accelerated certification process at the beginning of the pandemic and is no longer accurate.

Covid tends to show up in throat samples much earlier than in nasal swabs, which is why many Pluslife users perform a throat swab or combined nasal and throat swab to detect infection as early as possible.

In the Imperial College Human Challenge study, almost all patients had detectable virus in their throats 1-2 days earlier than in their noses. We marked the time delta with red bars:

This suggests that a throat swab or combined nasal and throat swab will have the best results.

A good time to swab is after getting up before breakfast. Nasopharyngeal swabs also work, but require special knowledge and are not necessary for an accurate test result.

We recommend swabbing the throat as well as the cheek and under the tongue. It is important not to eat or drink anything at least 30-60 minutes beforehand to avoid interference. Avoid acidic foods.

Are pool tests possible?

Yes, many Pluslife users have had good experiences with small pools (3-4 people maximum). The risk of inhibitors and thus an invalid result increases with each additional person. The liquid must also not become too thick, otherwise it can no longer flow through the small capillaries on the test card.

For pools, individual swabs are extracted one after the other in the buffer solution and then tested normally. If the overall result is positive, swab again and test individually.

It is also worth considering in advance how a positive pool would be handled. In the event of a positive test, it takes a long time to resolve a large pool. If possible, consider using additional devices instead of increasing pool size.

Can I store samples and process them later?

As far as we could tell, samples should be processed immediately.

Under no circumstances should the sample be stored in the Pluslife buffer solution. The buffer solution is aggressive and the sample should be processed within a few minutes after extraction, otherwise the RNA will decompose and will no longer be detectable after some time.

If there is no other option, the swab should be stored in a fridge in a plastic bag or in an empty protective tube to protect it from drying out.

Are the buffer solutions of different test kits compatible?

The buffer solutions are labeled (e.g. "Extraction buffer 01"). If the type of buffer and the expiration date are identical, the buffers are interchangeable.

For example, it is possible to perform both a Covid and a Flu/RSV combination test with the contents of one tube. However, this requires two devices so that both tests can be started immediately, as the sample is not stable in the buffer solution.

The test solution "gels" and can no longer be transferred

It occasionally happens that the liquid in the test tubes gels. Various factors can contribute to increased sample buffer viscosity.

The cells introduced into the sample are lysed in the liquid. During lysis, DNA and RNA contained in cell nuclei and cytoplasm are released. These molecules are long-chain and can be very viscous in high concentrations, which makes the solution more viscous. This occurs particularly when too much material is introduced.

It is thought that small amounts of blood, which contribute to the viscosity through the introduction of clotting factors such as fibrinogen, may also play a role. Users have reported that it can be helpful to unscrew the cap if the liquid would otherwise no longer fit through the filter.

The test should be repeated with a new swab if the fluid gels. It may be helpful to avoid a nasal swab and just swab the throat instead.

Can I test for other pathogens?

Yes, Pluslife sells a variety of different test kits. Tests for Covid, influenza, RSV, Strep A and more are available from Altruan. More details can be found on the manufacturer's website.

For tests other than Covid, it is necessary to use our app so that the test is carried out correctly and the individual results can be displayed for combination tests.

Can nasal sprays interfere with the tests?

The interaction with nasal sprays such as VirX and Bioblock is unknown.

When using nasal sprays, an interval of at least several hours should be maintained or a nasal swab should be avoided altogether.

I've been positive for 20 days, am I still contagious?

Current studies not provide a clear answer to this question.

Due to their sensitivity, molecular tests such as PCR or Pluslife are of dubious utility for determining the end of an infection. They can measure the presence of (very small amounts of) viral RNA, but can only provide a rough indication of the viral load and no indication of contagiousness.

A Pluslife test can be positive even if the viral load is very low and there is no longer any risk of infection (days to weeks). The course of the disease is very individual. The decision should therefore be made according to a clinical evaluation and not purely on the basis of the test result.

Do the combination tests have disadvantages compared to individual tests?

Yes, with combination tests there are fewer channels available per test, which reduces sensitivity. The Covid/Flu combination tests, for example, have an LOD of 1000 copies instead of 400. For early detection of Covid, we recommend individual tests.

For clinical diagnosis, the difference is negligible.

Should let the swab soak in the buffer tube, like with rapid tests?

No, the manufacturer specifically advises against it. After thoroughly "squeezing" the swab, the test should be started immediately (within at most five minutes).

Can I use a vortex mixer?

Yes, the manufacturer states that if you happen to have one (such as in a lab), you can use it for mixing the buffer tubes as well as for the test cards. Do it briefly and gently.

It is not necessary to use a vortex mixer, but it can simplify the process considerably and improve the reproducibility of your results, especially for high throughput testing.

The liquid has already flowed into the chambers before I pushed in the lid.

This is normal and harmless - the pressure exerted on the test card when it is screwed shut is usually enough to force the liquid into the chambers. Nevertheless, always press in the lid, even if it appears unnecessary.

Tiny air bubbles have formed inside the chambers.

Tiny air bubbles are normal and harmless. Large air bubbles can disturb the test procedure - if in doubt, discard the card, use a new test card and be more careful when filling it.

After testing, there are always small bubbles in the chambers, this is also normal.

Liquid level has dropped below the two dashes.

This is normal. The chambers already fill before the lid is pressed in. As long as the liquid level was between the lines directly after filling the card, you're good! Do not add any extra fluid afterwards.

There is no liquid in the chambers.

Looks can be deceiving at a first glance. The chambers can look empty when they are filled entirely.

If there is really no liquid in the chambers, the sample was too thick. Resample and, in the case of a pool, reduce the number of pool participants.

The powder does not dissolve

The powder only dissolves completely during the test.

The white lyophilized balls are broken before testing

The breakage of the balls does not affect the test results. As long as the test card is within the validity period, and the appearance of it is normal, the ball's shape will not affect the test.

Can I carry the device with me?

Yes.The manufacturer recommends transporting it in the original packaging to avoid damage from shocks.

The device is a solid-state device. It contains neither moving parts nor any transport safeties.

Nevertheless, the electronics are not indestructible. Strong shocks, vibrations, extreme heat or cold, condensation and similar mischief can damage the optics or the circuit boards. When transporting, pack it well and avoid exposing it to any harsh environments.

For how long will the LED on the device display the result?

The device does not switch off automatically, the result would - in theory - still be readable days later.

However, the test card should be removed as soon as possible after the test, as the heater does not turn off after the test and some liquid will slowly evaporate. This is especially important for positive tests due to the risk of DNA contamination (see above).

Are any components of the kit toxic?

The exact chemical composition of the kit is not known. The manufacturer states that the buffer fluid is corrosive and contact with the skin should be avoided, and while brief contact is harmless, strongly recommends immediately washing off any spillage with water and soap.

We recommend treating the kit like you would treat a strong household cleaner. Use protective gloves and goggles, keep away from children and pets.

Can I use the test cards beyond the expiration date?

The manufacturer strongly recommends not to use expired test cards.

We have also carried out our own tests and can confirm that expired tests no longer work properly and can even be false negative.

The fresher the test kit, the better it works. It is therefore not advisable to stockpile test kits for a long period of time. Fresh batches are constantly being produced, it is better to order more frequently.

How can I tell whether my test cards are defective?

If the reaction does not work at all because the enzymes are no longer active enough or the sample contains interfering substances (inhibitors), the internal control would not respond and the instrument would report an invalid test. The internal control therefore guarantees, to a some extent, that the test cards are still OK and will detect high viral loads.

However, it might be possible for the enzymes to degrade - for example, due to incorrect storage - but without failing entirely. In this case, the (highly concentrated) internal control would still work, but sensitivity at very low viral loads would be reduced. We don't know whether this is something that can happen to Pluslife assays. Overall, it is safe to say that kits which aren't expired and were stored appropriately will have preserved their original sensitivity.

Can I operate the device with other power supplies?

Yes - any high-quality power supply unit with an output of min. 3A/15W is suitable. The device is powered via normal USB.

The device is very sensitive to electromagnetic interference. It works best when completely disconnected from the mains on a power bank (e.g. from Anker).

Laptops, smartphones and similar power sources often work as well, but do not always provide enough power and should be avoided.

The device beeps several times after switching on and does not work

This means that the heater has not reached its target temperature. This may be due to a defective power supply unit, inferior cable or even a defective device.

Early versions of the Pluslife Minidock often have problems with defective heaters. We recommend that you contact whoever you bought it from.

Where can I get replacement cables?

Unfortunately, Pluslife does not use a normal USB cable, but "USB to round plug". Such cables are commercially available, but not too common.

The size of the round plug (5.5 x 2.5 mm, male, DC 5525) and the polarity - minus outside, plus inside - are important. The length of the cable should be max. 1.5m with rating for min. 3A/15W.

Altruan sells replacement cables.

Can I use other/additional swabs, for example for pool tests?

Some materials can interfere with the reaction, the manufacturer therefore recommends using only Copan FLOQswab swabs, as these have been tested extensively.

The correct FLOQswabs are available from Altruan (the product image is wrong - don't worry). We recommend using these swabs for pool tests.

Thinner FLOQswab swabs for nasopharyngeal swabs are also available, such as these fancy expensive ones from Praxisdienst or your preferred medical supplier. The "normal" thick swabs are also available with a protective tube, which can be useful when testing several people.

If it is not possible to use the original swabs, other swabs made of flocked nylon might also work - however, the manufacturer has not tested these. Cotton, calcium alginate and coiled (instead of flocked) swabs are generally unsuitable.

Why is a positive result displayed faster than a negative result?

In a LAMP reaction, DNA is amplified until the strength of the optical signal exceeds a certain threshold, similar to the cycle threshold (Ct) value in PCR.

The higher the viral load, the earlier the exponential growth phase begins.

The device reports the positive result immediately after the threshold was exceeded. However, as there is no such clear indicator for a negative result, the device simply waits and then reports a negative result as long as the internal control has worked and none of the target reactions are positive.

On average, it takes about 10-15 minutes for a positive sample to be reported. Always wait for the entire duration of the test: a weakly positive result can take up to 30 minutes to be reported.

Does Pluslife recognize current variants?

Covid tests generally detect so-called "conserved epitopes", i.e. parts of the virus that do not mutate frequently. Therefore, new variants rarely cause false-negative results. Most recently, this happened with Omicron, which was no longer recognized by some single target antigen tests.

PCR/LAMP usually use multiple targets, so if one of the targets mutates, the other target(s) will still be detected. In the case of Omicron, the so-called "drop out" (i.e. failure of one of the targets) even made it possible to distinguish easily between Omicron and Delta in some assays.

Pluslife targets both N and ORF1ab gene sequences, and is therefore considered robust against mutations. The manufacturer declared on 20/09/2023 that Pluslife recognizes current Omicron variants incl. "Eris".

Can I power the device via its USB-C port?

No, you can only power the device via the round plug. The USB-C port is for data only.

Do I have to turn off the device using a long press on the button, or can I just unplug it?

Unplugging works just fine.

Rapid test positive, but Pluslife negative

If, after a positive rapid antigen test, a follow-up Pluslife test is negative, we recommend repeating both tests several hours apart to exclude stochastic effects and errors. If available, use different lots of each test.

Pluslife is more sensitive and specific than rapid tests and a repeatably negative Pluslife result is therefore more conclusive than a positive rapid test.

We are personally aware of cases in which a symptomatic respiratory infection (of unknown cause) caused false-positive rapid tests in several individuals. In one case, RT-qPCR was performed in addition to Pluslife, which confirmed the negative Pluslife result.

The RKI has confirmed that both rhinoviruses and bacterial pathogens can lead to false positive results. There are isolated case reports in the literature (et al.). The exact frequency and mechanism of action are unknown, but it appears to be relatively common. Since the manufacturers of rapid tests exclude cross-reactions with other respiratory pathogens in vitro in quality assurance, we hypothesize that the mucosal immune response itself is causally involved and might interfere with the response.

In a series of experiments we have ourselves confirmed that many rapid tests are highly sensitive to acids and even small amounts can overcome the acid regulation of the buffer solution, cause nonspecific binding and thus false positive results due to physical effects. Especially in young children with reflux, this possibility should be considered in addition to other interfering substances.

The authors would like to learn more about this phenomenon and we will cover the cost of a respiratory multiplex PCR panel for false-positive rapid tests with negative Pluslife results. Our e-mail address is on the bottom of the page.

How do rapid antigen tests work?

Rapid antigen tests are based on binding the antigens - i.e. viral proteins, not RNA - with special antibody complexes and thus making them visible to the naked eye.

The sample is first stabilized in a lysis buffer, which dissolves the proteins from the virus ("lysis") and raises or lowers the pH of the solution to a certain value ("buffer").

The buffer solution is then dispensed onto the test strip.

Viral antigens first bind to mobile antibodies at the beginning of the test strip, which are marked with a colored marker (usually Colloidal Gold).

These antigen-antibody-gold complexes then bind to another set of antibodies fixed in place on the test line:

This method is prone to false positive results, since antibodies can also bind to each other or to any other proteins under non-optimal conditions such as incorrect pH and other interfering factors. With modern RT-qPCR or LAMP (with probes), this is much less likely: both primer and sample must bind to specific target DNA sequences, which - unlike the protein interaction - cannot easily happen due to purely physical effects.

This also explains the big difference in sensitivity: there must be enough viral protein in the sample to be able to see the resulting complexes with the naked eye.

Rapid tests are therefore only effective when a high viral load is present in the sample. They are of limited use for early detection and prevention of infection.

virus.sucks app

The virus.sucks team has developed its own app for reading raw curves. It's a web app that works on almost any device with a Chrome or Edge browser.

Like the official applications, the app makes it possible to use test kits other than the Covid tests and to display the individual results.

Unlike the official apps, it also displays the raw amplification curve:

Manual interpretation of the amplification curve enables a much higher level of confidence when using the tests as well as higher sensitivity. We will soon publish detailed instructions on how to interpret the curves. There are already some examples on Twitter, such as on air bubbles, very weak positive results and the dynamics of the reaction.

Compatibility

The app can be connected to the device via Bluetooth or USB-C and works on Windows, macOS, ChromeOS or Linux in Chrome, Edge, Vivaldi and other Chromium-based browsers.

Only Bluetooth works on smartphones. On iOS, the Bluefy browser is required.

Some very old Pluslife devices only support USB and no Bluetooth.

Desktop-Linux

On Linux, start Chrome with --enable-features=WebBluetooth to enable Bluetooth. The experimental flag in about:flags has been removed in Chromium 121 (for whatever reason).

For the serial console, it must be ensured that the current user is allowed to read and write the device (e.g. /dev/ttyUSB0). With most distros, it is sufficient to add the user to the dialout group.

Using the app

Simply connect the app to the device and switch on the device as normal.

Then start the test not by pressing a button on the device, but after selecting the correct kit via the app. The test should be started at the same time as the test card is inserted into the device.

Keep the browser window and tab in the foreground during the test. Progress can be tracked in real time. If the test is negative, the control curve (channel 4) will increase exponentially after approx. 10 minutes, while the other curves will not change at all or only slightly. If the result is positive, several other curves will rise in addition to the control.

The evaluation of the curves is a tool for experts and is not strictly necessary for normal clinical use.

Once the test has been completed, the final result is displayed - just like on the device. For combination tests, the results per pathogen are also displayed.

Apps from the manufacturer

Pluslife also offers a range of applications for download, which can be connected to the device either via Bluetooth (smartphone apps) or USB-C (Windows).

Laboratories can use the Windows application to keep track of a large number of devices and assign the test results to individual samples.

We do not recommend using the smartphone apps, as they do not work reliably and are very difficult to install. Our own app offers a better alternative.

Change history

Only significant changes are listed.

12.03.2024

21.10.2023

20.10.2023

03.10.2023


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