The one of Asymptomatic carriers have been one of the biggest challenges in controlling the COVID-19 pandemic.
These people, although they do not develop any signs of the disease, they can to be contagiousing to others without knowing itTherefore, it is essential to identify them.
It is estimated that at least one in 3 SARS-CoV-2 infections could be asymptomatic, according to a review of the available data published in May by Daniel Oran and Eric Topol, researchers at the Scripps Research Institute in the United States.
In a new study, published in the specialized journal eLife, a group of Chilean and British scientists claim to have developed a novel method for identify asymptomatic patients or presymptomatic, as a way to help reduce the spread of the virus.
His technique consists of take samples from cell phone screens of people, an idea that is low cost, non-invasive and with reliable results, according to the study.
“The big problem with COVID-19 is that many people walk down the street infecting it and do not know it,” Dr. Rodrigo Young, creator of this method and researcher at the Institute of Ophthalmology at University College London, tells BBC Mundo , in the United Kingdom.
That’s why, as Young explains, screening as many people as possible is an effective way to reduce contagion.
Several experts consulted by BBC Mundo agree that Young’s method can be very useful, but it also faces some challenges.
Asymptomatic patients may be infecting others without realizing it. (Photo: .)
PCR and cell phones
People who have COVID-19 can infect others from about 2 days before symptoms start and up to 10 days after, according to the UK’s National Institutes of Health (NHS).
Those who are infected can pass the infection to others, even if they have mild symptoms or no symptoms, explains the NHS.
Tests Traditional PCR, those done through the nose, are an effective way to know if a person is infected with SARS-CoV-2, even if they do not show symptoms or are in the contagious stage of the virus.
These tests, however, can be expensive or uncomfortable for the patient.
Therefore, Young thought that a good alternative could be to take the samples from the screens of people’s cell phones.
“I realized that the key is not to take a sample from the person, but from something that is a reflection of the person ”, He says.
How we spend so much time playing and talking On our phones, what’s left on the screen can be a good reflection of what’s inside us, Young explains.
When talking on a cell phone, we can leave traces of the virus on the screen. (Photo: .)
The test, which they called PoST (Phone Screen Testing, in Spanish Telephone Screen Testing), consists in that, instead of introducing a swab in the person’s nose, what they do is pass the swab over the screen of his cellphone.
In this way, they can detect if there is traces of RNA, that is to say, genetic material of the virus, on the cell phone screen.
In other words, it is doing a PCR test on the cell phone.
Traditional PCR and PoST
To test their method, Young and his team examined close to 1,200 people, who underwent both the nasopharyngeal PCR test and the PoST method.
The result was that with the PoST method they detected all the people who, according to the nasopharyngeal PCR, had high viral load.
People with a high viral load are the most likely to infect others.
The agreement between what the nasopharyngeal PCR showed and the PoST method was between 81% and 100%, according to data from the study.
For these trials, Young had the support of the University of Chile and the Great Ormond Street Hospital in London.
Nasal PCRs can be uncomfortable for the patient. (Photo: .)
It does not replace traditional PCR
Young clarifies that the PoST method does not replace to a nasopharyngeal PCR test. The PoSt is a prediagnostic test.
Nasopharyngeal PCR can detect all infected people, contagious or not.
With the PoST, on the other hand, only those with a high viral load can be identified.
This means that the PoST can be escape people who are sick, but who are no longer contagious.
“If that person has not entered or has already left the stage where the virus is contagious, they will not spread the virus on the cell phone “Young explains.
“The PoST does not replace the nasopharyngeal PCR, but it does allow detecting sick people who, because they do not have symptoms they would not do a PCR nasopharyngeal ”.
“This is a test to see if one is contagious ”, says the researcher.
So, if a cell phone scores positive in the PoST test, the owner of that phone must do a traditional PCR to confirm that you are infected with SARS-CoV-2 and may be infecting others.
The PoST test can be an early warning system to detect people with a high viral load. (Photo: Diagnosis Biotech)
In the same way, if the PoST test gives negativeIt does not mean that the person is not infected, but that they are possibly not infecting others.
According to Young, many of the costs of traditional PCR are associated with the logistics required to perform them, the personnel, the protective material and the supplies.
The researcher explains that his method allows Lower costs in the same way that buying the ingredients to make a pizza at home is cheaper than buying it made.
“We buy the supplies for PCR detection separately, instead of buying kits with clinical certification where everything comes prepared,” he says.
“The components we use are the same as those used in clinical kits and they are also approved by the Centers for Disease Control and Prevention (CDC) ”.
“We can do this assembling kits because we are experts in PCR and molecular biology techniques,” he says.
Consulted by BBC Mundo, several experts who were not involved in this research agree that the PoST method is a good idea.
Identifying presymptomatic or asymptomatic people is key to fighting the pandemic. (Photo: .)
“This test can be useful as a system of early warning, when it is used followed by a conventional test ”, tells BBC Mundo Emanuel Goldman, professor of microbiology, biochemistry and molecular genetics at Rutgers University.
Goldman, however, warns that it is important to take into account that the fact that there are traces of RNA of the virus in the cell does not mean what the person is infected.
“There may be other forms where viral RNA could end up on the surface of a phone, “says Goldman.
For example, someone might have touched a surface with virus RNA and transfer it to the cell surface.
The RNA it’s just a sign that the virus was present in a place. That, according to Goldman’s explanations, means that the RNA in the cell phone is from another person, or that that person has transferred it without even being infected.
Another possible scenario that Goldman sees possible is that a person no longer has the virus, but traces of the virus, the RNA, are still on the surface of their cell phone. In this case, for example, the PoST could generate a false positive.
For reasons like these, the PoST “should not be considered a substitute of the nasal swab or saliva test, “insists Goldman.
“If the phone test is positive, then a conventional test should be done to check“.
A similar view is held by Rosanna Peeling, Professor of Diagnostic Research at the UK School of Hygiene and Tropical Medicine.
Some experts warn that there could be several reasons to explain why there are traces of the virus on a surface such as a cell phone. (Photo: .)
“What about people who don’t talk to the phone close to his mouth? Many people use it with hearing aids while they have a cell phone in their pocket ”, asks Peeling during the interview with BBC Mundo.
“There’s a lot possible explanations to a result obtained by taking samples from a phone… it depends on how the person uses the phone, who has been in contact with the device, someone else may have taken it or coughed on it ”.
Although it is not documented in the study, Young affirms that the results of his tests show that the probability of third parties contaminating the cell phone of the person taking the test It is low.
“We concluded this because we were able to test entire families who live together and sometimes exchange cell phones, ”he says.
“In these families, only the person who also tested positive by nasopharyngeal PCR gave a positive PoST test.”
Young’s interpretation is that for a sample to score positive, it must accumulate enough quantity on the screen to be detected, that is, that other person should use the cell phone more frequently to deposit traces of the virus that are detectable.
Young, however, cautions that they need a larger number of cases in order to have a more accurate conclusion.
The creators of the PoSt trust that applying it in a massive way will help to return to normality. (Photo: .)
On the other hand, the study showed that although people clean the cell phone Before testing, the PoST result is not affected.
“The liquids that people use to clean their cell phones destroy the virus, but the corpse is left there, and that is what we detect ”, he says.
The PoST method is already being used in some companies and schools in Chile, as part of an active search service for people who are infected but do not show symptoms.
According to Young, this strategy is a way to maintain continuity of operations of these institutions and avoid outbreaks.
The researcher explains that he is in talks with the health authorities to define the regulatory framework that covers them and apply the tests massively.
At this point, Peeling mentions that the logistics of massively implementing PoST can be challenging.
“It’s like adding another layer”says the expert, referring to the fact that in many places it is not easy to install traditional PCR test points, as well as adding the PoST prediagnostic test point.
In any case, Young mentions, for example, the possibility of make machines that are located in different parts of the cities, where each person can enter their telephone number and receive the results via text message.
“The important thing is to implement it on a large scale as soon as possible since it could help a lot to stop the pandemic so that we can return to a normal life “Young concludes.
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