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, Metrix or 3EO, 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, simply do it 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.
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 comparable to lab PCR tests, which typically have LODs between 50 and 1000 copies/mL, depending on the quality of the assay. It has been independently verified.
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:
Compared to conventional rapid tests, which rely on direct detection of the pathogen, Pluslife tests - like other molecular tests - rely on exponential amplification of genetic material and can detect pathogens at lower levels and therefore earlier during the exponential amplification process, often before viral load is high enough for transmission.
Molecular tests such as Pluslife are very sensitive and can enable social interactions that would otherwise be too risky, depending on personal risk tolerances. However, keep in mind that - like any other method of relative risk reduction - they cannot guarantee 100% safety, and the absolute, effective risk greatly depends on your specific circumstances and the probability of someone being infected in the first place ("pre-test probability"). Which level of risk is acceptable or not is an individual decision and there are no "one size fits all" approaches to risk mitigation.
Device and tests are sold by Altruan. For non-commercial use, Altruan offers special conditions to our community - email us for details (discount [ät] virus.sucks).
This website is independent and non-commercial. We do not receive any commission or other compensation.
Start the test immediately after the card is inserted into the device. The biochemical reaction starts as soon as the card is inside the device, regardless of whether the button has been pressed. If you wait too long, you will get an invalid or false result. This is very important.
The device should not be placed in the sun or exposed to direct sunlight during the test. Bright light interferes with the sensitive optical sensors inside the device. Do not open the lid during tests.
Avoid extreme heat or cold while operating the device. Condensation inside the device destroys it.
We recommend using a power bank (such as from Anker) instead of the supplied power supply unit.
Make sure to wait for ~15 seconds after screwing on the lid before pressing the top of the lid. This ensures that the liquid has enough time to fill the reaction chambers.
Once removed from the packaging, avoid exposing the test card and the buffer tube to bright light for extended periods. Molecular probes are very sensitive to light.
Do not forget to switch off or unplug the device - its heater will happily continue to heat. There is no automatic shutdown.
Lightly moving the device during a test (such as in a car) is okay, but be careful.
Do not overdo it when shaking the buffer tube and the test cards, otherwise foam and air bubbles will form, which can lead to invalid results. After thoroughly "squeezing" the swab in the tube, it is sufficient to invert and gently flick the tube several times to mix reagents.
If visible foam or air bubbles have formed, let the tube briefly rest while standing upright before transferring the fluid into the test card to prevent bubbles from entering it.
Process the sample material as quickly as possible: the viral RNA dissolved in the lysis buffer degrades relatively quickly. If necessary, store the unprocessed sample in the refrigerator or - ideally - freezer if immediate processing is not possible. Always insert the test card immediately into the instrument after transferring the sample and never store it.
Keep kit components out of the reach of children.
Make sure that the lid of the test card is properly secured.
Check test cards for damage or chips before using it.
Keep electronic devices which generate strong electromagnetic fields - such as mobile phones or radios - away from the device while a test is running.
Do not touch the surface of the test chambers on the cards. Oils on the fingers can impair the optical readout of the test chambers.
Wear disposable gloves and goggles. The buffer liquid is corrosive. If liquid does get on the skin, wash immediately with soap. In case of contact with eyes, rinse with clean water immediately and seek medical advice.
Put used test cards (esp. positive ones) into one of the safety waste bags that come with the kit and dispose of them immediately. Normal household waste is fine, it is not hazardous.
Do not re-test a card which had an invalid result, but try again with a new test card.
Remove the test cards promptly after the test, otherwise some of the liquid inside will slowly evaporate despite the lid. This applies especially to positive tests.
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 then become useless in contaminated rooms or for persons exposed to environmental contamination.
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.
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.
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.
It's also possible to get false positive results from improper usage of the device - such as opening the lid during amplification, inserting the test card after the test is already running, or removing and re-inserting the card during a test.
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 entirely, 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.
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.
There are a number of possible reasons for invalid tests:
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.
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).
While there is no "golden rule", many users have successfully avoided household infections with a re-test window of ~12 to - at most - 24 hours.
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.
The manufacturer told us that both nasal and throat swabs will work, and mentioned that 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:
While there is some uncertainty due to the lack of clinical studies with throat swabs, the data suggests that a throat swab or combined nasal and throat swab is best for early detection.
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.
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 multiple devices instead of increasing pool size.
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. Freezing is best, but make sure to fully thaw the sample before processing.
Check the label on the tubes - it will indicate the type of buffer (such as Nucleic acid release agent 01). If it's the same buffer, it can be used interchangeably. For instance, SARS-Cov-2 tests and FluA/FluB/RSV tests use the same buffer (01), but StrepA tests do not (02). Always re-check the label on your specific lots to make sure they are compatible and make sure the buffer isn't expired.
If the buffers are identical, you can run different tests in parallel with just one sample. There is enough liquid in the tube for two tests. However, we recommend using multiple devices to run both tests at the same time to avoid exposing the sample to the buffer solution for too long. If you have only one device, use a fresh sample and a new tube for the second test.
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.
Yes, Pluslife sells a variety of different test kits. While this document focuses on SARS-Cov-2, tests for influenza A/B, 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.
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.
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.
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 usually negligible.
No, the manufacturer specifically advises against it. After thoroughly "squeezing" the swab, the test should be started immediately (within at most five minutes).
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. Vortexing too much can destroy the reagents.
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.
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 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.
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.
Unfortunately, the lines can be hard to see. Good overhead lighting helps. You can also mark the lines with a thin permanent marker ahead of time.
We asked Pluslife whether they could add markings in the factory, but unfortunately, it would make the tests more expensive since extra machines are required.
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 only dissolves completely during the test.
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.
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.
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).
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 that may be toxic. Use protective gloves and goggles, keep away from children and pets.
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 buffer solution degrades over time and becomes more acidic.
The fresher the test kit, the better it works. We recommend against stockpiling more than a six-month supply. Fresh batches are constantly being produced, it is better to order more frequently.
SARS-CoV-2 tests expire 12 months from the manufacturing date. When you order SARS-CoV-2 tests from Altruan, you usually receive a fresh batch - they're in high demand and don't stay in the warehouse for long.
Other tests and tests from distributors other than Altruan may have shorter expiration dates when you receive them.
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.
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).
Low-quality power supplies can severely interfere with the device's electronics. Refer to our connection troubleshooting article for advice on power supplies.
Laptops, smartphones and similar power sources often work as well, but do not always provide enough power and should be avoided.
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.
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 2.1 mm, male, DC 5521) 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.
Some materials can interfere with the reaction or have the wrong elution volume, which is why the manufacturer recommends using only Copan FLOQswab 502C swabs, which have been tested extensively.
They're available from Altruan (ignore the incorrect picture). Many local medical suppliers have them too, it's a very common brand and widely used for diagnostics.
Thinner FLOQswab swabs for nasopharyngeal swabs are also available. In Germany, they're sold by Praxisdienst. Most local suppliers should have them. The "normal" thick swabs are also available with a protective tube, which can be useful when testing several people to avoid collecting too much material.
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 and it's impossible to know which brands are problematic. Pluslife's release agent is unusually aggressive and Pluslife mentioned that some brands had issues where the glue would dissolve. Cotton, calcium alginate and coiled (instead of flocked) swabs are generally unsuitable.
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 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.
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".
No, you can only power the device via the round plug. The USB-C port is for data only.
Unplugging works just fine.
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.
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.
It depends on whether the vaccine contains the pieces of the viral genome which the test targets.
For SARS-Cov-2, mRNA (Novavax, Pfizer), protein subunit vaccines (Novavax) or viral vector vaccines (AstraZeneca) encode only the spike protein, not the entire virus. Pluslife does not look for the Spike gene, which means that false positives for SARS-Cov-2 are impossible with these vaccines.
Live-attenuated vaccines contain "real" virus, which can cause false positives. For instance, many influenza vaccines are live-attenuated vaccines, which can result in positive FluA/B tests.
Yes. It's a convenient way to test the device and troubleshoot connectivity issues.
The service life is not an expiration date, but the expected lifetime of the device guaranteed by the manufacturer in a professional environment. In practice, it will most likely last much longer than the indicated minimum lifetime, it just won't be guaranteed or certified by the manufacturer.
According to Copan, the expiration date on swabs is related to the sterilization process. Sterilization is only guaranteed for a certain period. Expired swabs should work just fine.
For SARS-Cov-2, incubation times are relatively short. A good rule of thumb is to start testing after 24 hours and continue testing for 4-5 days during the possible incubation period.
The vet minidock is technically identical to the human minidock. However, they're not approved or validated for human use, so you're completely on your own if you chose re-appropriate them for human use.
Minidocks for other uses may be configured to run tests other than SARS-Cov-2 when you press the button on the device to start a test, rather than using the app. Make sure to always use the app to start your tests to ensure that the correct program is used to evaluate test results.
It depends - the test program doesn't just influence the way the results are interpreted, it also affects the temperature steps used by the device. Choosing the wrong test may lead to incorrect results.
SARS-Cov-2 and SARS-Cov-2/FluA/FluB combination tests use very similar temperatures, so it's probably okay if you mixed those up. However, you'll have to interpret results manually from the fluorescence curves. If you don't know how to do that, it's best to repeat the test with a fresh sample.
The tests have not been validated with saliva, so we don't have accurate data to answer this question.
The good thing about molecular tests is that they're highly sensitive, so they are more tolerant to suboptimal sampling techniques than antigen tests. Anecdotally, testing saliva works well and can be a good alternative when compliance is an issue (such as when testing little kids), especially if better compliance means testing can be done more frequently.
Pluslife has confirmed that the Flu tests work for H5N1. However, you won't know whether it is H5N1 or another influenza strain.
While this is a common problem with other molecular tests such as Lucira, false positives due to contamination or wrong pH are highly unlikely with Pluslife. We have never seen it happen.
The probe-based RHAM technology which Pluslife uses is highly specific and very resilient against non-specific amplification, unlike most LAMP assays. Both the primer and the probe have to bind to their target sequences for amplification to occur.
However, a very low pH value can inhibit the reaction and lower its sensitivity, potentially leading to false negatives at low viral loads.
Yes, blood will interfere with the test and should be avoided.
Studies with the manufacturer's involvement:
Independent studies:
Herrmann, Laura, Juliana Breuer, Tuan Ngo Duc, Nicole Thomé, Fatemeh Ghazaani, Sundrela Kamhieh-Milz, Julian Kamhieh-Milz, and Andreas Pfützner. “Comparison of the Diagnostic Accuracy of the Pluslife Mini Dock RHAM Technology with Abbott ID Now and Cepheid GenXpert: A Retrospective Evaluation Study.” Scientific Reports 14, no. 1 (2024): 13978 (doi.org/10.1038/s41598-024-64406-9)
Zhu, Dandan, Jing Huang, Bei Hu, Donglin Cao, Dingqiang Chen, Xinqiang Song, Jialing Chen, Hao Zhou, Aiqun Cen, and Tieying Hou. “Trial of the Pluslife SARS-CoV-2 Nucleic Acid Rapid Test Kit: Prospective Cohort Study.” JMIR Public Health and Surveillance 9 (2023): e48107 (doi.org/10.2196/48107).
Other sources:
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.
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.
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.
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.
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.
The manufacturer's app do not display the amplification curve.
For SARS-Cov-2 tests, at least two channels must be positive for the device to recognize the final result as positive.
When you use our app, you can see the raw data from the amplification, which means that it's sometimes possible for an expert user to identify positive results before the device does. This is the case when at least one of curves other than the internal control show clear signs of exponential increase (sigmoid shape, like the control reaction).
When there's clear signs of amplification on a single target channel, it indicates a weak positive result with low viral load, even when the device returns a negative result. For example, this is a positive result:
There are multiple possible reasons for weak positive results: An early warning about a fresh infection, viral fragments from a past infection (which can take weeks to fully clear), or even a failed infection which was successfully cleared by the immune system.
Rarely, weak positive results can also appear in the complete absence of an infection. We don't know why - it could be artifacts, low-level DNA or RNA contamination, or probe degradation/unspecific amplification.
A very slight, linear increase in some or all of the reaction channels is normal and does not indicate a positive result.
Air bubbles (incompletely filled reaction chambers) can cause invalid reaction curves which increase suddenly or jump around, due to optical refraction effects. These can even cause false positive results.
Make sure that the chambers are fully filled with liquid. Very small air bubbles tend to be OK, but large air bubbles will cause problems (see above for an example of an air bubble).
After screwing on the lid, make sure to wait ~15 seconds while some of liquid moves to the reaction chambers. Then gently press the top of the lid to force the rest of the liquid into the chambers. Doing it too quickly is the most common cause for air bubbles.
Fortunately, it is easy to distinguish an air bubble from a real amplification result. A true amplification result has a sigmoidal shape and will never increase or decrease suddenly:
This is an air bubble:
Generally, no. Pluslife assays are optimized for qualitative (yes/no) detection rather than quantitative results.
In a clinical report from Israel, time-to-positive did not correlate with RT-qPCR Cq value over most of the relevant range. Only very low viral loads resulted in higher time-to-positive:
(data from the report, graphic our own)
Data from our own experiments confirmed this. In our experiments, time-to-positive was correlated to pH value much more strongly than viral copy number. Therefore, it is our opinion that Pluslife assays are not suitable for any kind of quantification.
There's a small exception: When only some, rather than all, of the target curves amplify (drop-out), the viral load is likely to be very low. However, that's not an exact science either. For reliable quantification, a quantitative RT-qPCR test is required.
| LED state | Meaning |
|---|---|
| Red blinking | Heating up |
| Blue steady | Ready to test |
| Blue blinking | Test is running |
| Red steady | Positive result |
| Green steady | Negative result |
| Red + green steady | Invalid result |
No. When a test is interrupted by a power outage or similar, the device will not remember the state of the test. Attempting to run the same test card again can lead to inaccurate results, even when the device displays a valid result, since the reaction occurs only once.
Unfortunately, the Bluetooth and USB connectivity to the Pluslife device is not always stable. This is a hardware issue, so there's not much we can do about it. Refer to our troubleshooting guide for tips on how to improve reliability.
When the app disconnects during a test, you can sometimes press "Reconnect" to re-establish the connection. If that doesn't work, you can restart the app and re-connect to the running test, but parts of the amplification graph will be missing.
Even if the app loses connection to the device, the test continues to run on the device and the result will be displayed on LEDs. You only lose the additional information from the app.
It always takes a few minutes for a real amplification reaction to start. If a curve starts going up immediately after the test starts (i.e. at minute zero), while the control reaction happens normally after a few minutes, it's an artifact and should be ignored.
It is particularly common in Flu, RSV and Strep tests.
If the control reaction is very flat (i.e. low reaction efficiency), it means that something has disturbed (inhibited) the reaction. The result is still valid, however, sensitivity might be reduced.
See above for potential causes. Repeat the test for optimal sensitivity.
Yes, this is possible. Open our Pluslife app in multiple browser windows - not tabs - such that all apps are visible on the screen. Then connect them to the devices one by one (you can use the serial number in expert mode to figure out which is which).
USB is more stable than Bluetooth.
