Tens of thousands of Brits who have been given Covid-19 may have mistakenly learned that they are free of the virus because of the tests used by the government.
Scientists in the United States used a saliva test and nasopharynx swabs to analyze the accuracy of nasal swabs that the patient had taken himself.
Nasopharyngeal swabs, which are only carried out by a trained doctor, are inserted so deeply into the nose that people choke, water their eyes or even cause nosebleeds.
Of 86 people with Covid-19, only 70 were swabbed. The nasopharyngeal swabs and saliva tests were also not perfect, but resulted in more cases – 80 and 81, respectively.
Although the researchers said it was not a large number of "wrong" results, any missed case can have ramifications.
If a person who is positive for Covid-19 gets a false negative result, they will not isolate themselves and can spread the virus to others.
The results could apply to nasal swabs provided by the government for test kits and transit centers across the UK. However, instructions also tell you to wipe your neck.
More than 11 million tests have been carried out across the UK, a significant part of which would have been carried out in-house.
Professionally performed nasopharynx tests are known to be uncomfortable because the swab has to reach so far back into the person's nose (Image: A man being tested in Surabaya, Indonesia).
Instructions from Public Health England for performing a DIY home test kit
The tests people do in transit centers or from the comfort of their own home are far less invasive than nasopharyngeal smears – which is considered the gold standard by scientists.
Instructions for using a single swab around the throat and nostril are included in the kit.
This can make people feel sick or tickle, but the swab is not pushed deep into the nostril to reach the nasal floor – as would be the case with nasopharynx swabs.
WHAT ARE THE DIFFERENT SWAB TESTS FOR CORONAVIRUS?
Nasopharyngeal swabs are used to detect respiratory viruses such as the flu and the new coronavirus.
According to the Centers for Disease Control and Prevention (CDC), this is the preferred choice for SARS-CoV-2 tests.
A long, flexible cotton swab is inserted into the nostril and along the nasal floor. This should be done slowly so that it is comfortable.
The goal is to reach the posterior nasopharynx, a cavity of muscles and connective tissue that is covered with nasal cells and mucus. It continues in the throat.
The swab is rotated several times to obtain enough cells.
The sample is then sent to a laboratory where it is tested to determine if the patient's cells are infected with the virus.
Coronavirus is an RNA virus, which means that it uses ribonucleic acid as its genetic material. A process called reverse transcription is required to transcribe the RNA into readable DNA.
A swab sample does not collect much RNA at a time, so a polymerase chain reaction (PCR) is used to quickly make billions of copies for analysis.
The DNA is stained fluorescent, which glows when the coronavirus is present, which confirms a diagnosis.
Anterior nasal swabs, which are read in the laboratory using the methods described above, can be performed by the patient using a shorter cotton swab.
The swab only has to penetrate to a depth of about one centimeter before being rubbed around the nostril wall.
The patient is less likely to feel sick or to produce a gag or cough reflex.
Experts say they have less contact with the mucous membranes, which are areas of thin tissue in the airways where most of the coronaviruses live.
Experts say that front nasal swabs have less contact with the mucous membranes, which are areas of thin tissue in the airways where most corona viruses live.
The instructions given to the British in the post tests say: "No force is required and you don't have to push far into your nostril."
One advantage is that they are less likely to cause a cough due to their lower invasiveness – which means that healthcare workers are less likely to be exposed to the virus.
Professor Paul Hunter, an infectious disease expert at the University of East Anglia, said the study results "suggest that these DIY tests are not as good and miss part".
He claimed that around 10 percent of the coronavirus tests that would have been detected in the nasopharyngeal swab test would be missed in the home test.
However, Professor Hunter told MailOnline that the study did not prove that the tests were useless and called for larger trials with the swabs currently used in the UK.
He said: "This study is fairly small and needs to be repeated with a larger number of tests, preferably in the UK, before we can draw any firm conclusions."
The study, which has not yet been published in a medical journal or reviewed by other experts, was conducted in Utah hospitals.
In a transit test center, 354 people took all three Covid 19 tests. They were instructed to wipe both nostrils, known as an anterior nasal swab test, into a tube, and then a doctor performed the nasopharynx swab.
Around 268 people consistently received a negative result. Eighty-six people scored either one, two, or three or the tests.
No single test gave 86 results, which proves that no test can always detect the coronavirus.
SARS-CoV-2 was detected in all three tests in 66 patients, which means that they no doubt had the virus.
However, 13 were found in only two tests, and seven patients obtained one test with a positive result.
If one of these 20 patients had had a single test, the result might have been negative.
The seven that tested positive consisted of two nasopharyngeal swabs and five saliva tests – which means that the nasal swabs never picked up the virus individually.
The results broken down how many results were obtained with each test method to determine that anterior nasal swabs were least likely to give a positive result.
The differences in the results "did not achieve statistical significance" because the numbers are so small, it says in the article about medRxiv.
However, the researchers wrote: “If you only rely on anterior nasal swabs, the infection can be overlooked in 10 to 11 patients compared to nasopharyngeal swabs or saliva.
"Missed Covid-19 cases have a serious clinical impact on isolation decisions in symptomatic 111 patients and are a missed opportunity to track contacts."
How nasopharyngeal swabs are done: Pediatric nurse Jessica Peck shared a diagram of how the coronavirus test is done on Twitter and said, “We have to smear that far to test you on # COVID19z. You may want to follow the medical recommendations and #StayAtHome. & # 39;
How Coronavirus Self-Tests Are Performed: The patient must insert the swab into the throat and then a short distance into the nostril to try to ingest the airborne viruses
When the researchers compared the tests, they found an “excellent match”. This means that in most cases the tests gave the same result – either negative or positive.
The results showed that when a nasopharyngeal smear was taken next to an anterior smear, the results were the same in 86.3 percent of cases.
If a nasopharyngeal smear was taken in addition to a straight saliva test, there was a 93.8 percent chance that the results were correct.
This, the researchers said, the highest number of cases would be found if nasopharyngeal swabs were combined with a saliva test.
SELF-SWABS FOR COVID-19 WORKS, STUDY SHOWS
Despite concerns, scientific studies have shown that self-tapping tests are actually accurate enough to diagnose viruses.
A study by researchers from the University of California at Los Angeles found that self-tests when trying to diagnose Covid-19 showed "comparable sensitivity".
This shows that both professionally made swabs and those made by humans received approximately the same proportion of positive cases.
This study, published online on April 15, was conducted on 45 people, 29 of whom were definitely infected with the coronavirus and had already been diagnosed.
It was found that 26 of these 29 patients were found in the monitored self-collection tests, while only 19 out of 29 (66 percent) were found in the unsupervised self-collection.
In the meantime, tests carried out by doctors have successfully identified 23 out of 29 positive cases.
In summary, the scientists said, "Monitored self-collected oral fluid and nasal swab samples that were performed similarly, if not better, than nasopharyngeal swab samples to detect SARS-CoV-2 infection."
Another study of generic respiratory infections found that nasopharyngeal swabs performed better than just a nose swab.
Researchers from the University of Turku in Finland tested the two types on 230 children with breast infections.
They found that using both methods together – the deep nose and nostril – 73 percent of the cases were successfully identified.
The nasopharynx smear alone found 19 percent of the cases, while only one nasal swab found only seven percent.
Her research was published in the Journal of Clinical Microbiology.
The researchers found: “In the past, nasopharyngeal smears were seen as a reference method for the detection of respiratory viruses.
In addition, anterior nasal swabs are routinely used for influenza nucleic acid amplification (NAAT) tests.
"However, the recurrent lack of swabs and personal protective equipment (PPE) has led to an evaluation of alternatives to NPS, including the use of self-collected ANS and saliva from patients."
The Ministry of Health and Social Affairs disproved the results and said the evidence shows that self-tests are "just as effective".
A spokesman told MailOnline: "Instructions for performing this type of test are included wherever individuals are asked to wipe themselves."
Scientists warned for the first time that self-tests may be less accurate in June after Britain began increasing its smear capacity in late April.
Dr. Andrew Preston, an infectious pulmonary disease specialist at the University of Bath, told MailOnline that flatter swabs in the nose and mouth weren't as good.
He said: "It is clear that the deeper the nasopharynx, the better it absorbs the virus."
Dr. Preston added: “I work a lot with whooping cough and we tilt the person's head back.
"We consider it an unsuccessful swab unless the eyes water. We see real, real problems with the sensitivity of the swab when wiping in the nose. & # 39;
In a clear warning of how self-tests could miss the infection, he said, "The further you go back, the greater the chance that you will get the virus."
Even nasopharyngeal swab tests performed by professionals are estimated to be inaccurate in up to 30 percent of cases because the way doctors perform them varies.
This is based on scientists' estimates, as the Ministry of Health does not publish data on the false negative rates of its tests.
It is not clear how inaccurate self-smears are, although they are done more than 60,000 times a day in the UK.
Professor Jon Deeks, a biostatistics expert at the University of Birmingham, said: "A single negative test result does not rule out the disease."
Nasopharyngeal swabs are believed to be more reliable because they can better identify traces of a virus.
They go much deeper into the nasopharynx, a cavity in the airways that connects to the neck.
Doctors receive a sample along the nasal floor near the mucous membranes – Areas of thin tissue in the airways where most corona viruses live.
Claire Cox, an ICU nurse working in Brighton, said in May that using the right technology was critical.
In a blog about patient safety learning, she wrote: "Simply wiping the inside of the nasal passage is not deep enough to check for the presence of the virus."
These swabs are known to be uncomfortable because they require an extra long cotton swab that needs to be pushed and twisted into the back of the nostril.
They can choke people, make their eyes water, or even cause nosebleeds – but they're considered the most accurate way to diagnose Covid-19.
I tested myself and was tested by a doctor – there is no way to get it right
"Is it far enough?"
What sounds like a one-liner from a hackneyed comedy, maybe Carry On Covid, must have been heard across the country in the past few weeks when people with coronavirus symptoms tried to test themselves, either in a transit center or at home.
It was what I said when my wife and I were in our car this week. Each of us felt well below the weather and on a short backup when we tried to use the government swab test.
For those who haven't had the displeasure yet, you need to put a swab like a giant cotton swab in your throat, slide it over your tonsils for about 10 seconds, and then about an inch over your nose or until you feel resistance – and turn it around like an old-fashioned radio button.
The instructions are in diagram form and appear to be straightforward, even if the front seat of a car hardly has the sterile environment you want for such tests. It's even recommended to use the car mirror to see how you insert the swab.
The neck area seemed fairly simple, if uncomfortable and with a little gagging. But then came the hard part – how can you tell if it got into your nose enough?
I tore myself open when I took the plunge and pushed it into my nose before I let out one of the biggest sneezes I've ever made. It was uncomfortable, but not a big deal.
My wife turned hers around a few times and said, "This is as far as it goes. My nose can't be as big as yours. & # 39;
I was pretty confident that I had done it right, but she had misunderstood. I was not thanked for pointing this out.
No one was watching us to make sure we did it right. After all, a false negative diagnosis could lead us to infect people on the street.
After about 36 hours, our results came back – both negative.
This seemed strange since we have most of the classic symptoms – loss of smell, fever, sore muscles, sore throat, nausea, shortness of breath. Everything except the cough.
So we hired a doctor through a private clinic to do a similar swab test.
And what a difference. Who would have thought that you could touch the back of the head through your nose?
My wife had wrongly thought that it would go no further. It went much further, although the doctor needed at least four attempts because of her “slim nasal passage”. Maybe that's the new thigh gap during lockdown.
He told her that he hoped to get a large enough sample, but was still not convinced that it had worked properly and that she should rely on his clinical diagnosis instead.
I was wrong to push the swab up my nose. It goes in horizontally. Not to the top of your nose where you feel blocked with a cold, but along another passage to your throat.
At least that's how I felt there. After all, I'm not a doctor.
It's not exactly painful, but surprisingly uncomfortable and contradicts everything you think is possible. Every second I thought, "Stop, stop, you're going to pop something."
When he wiggled it around, I thought I'd suffocate.
It scratched my inside, made me stutter and cough, and wondered how it was possible to achieve this.
I am not asking anyone to do this successfully. Some people I spoke to after the drive-through test said, "It's easy, it only took a few seconds." My answer to that is that you didn't do it right.
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