Thermal screening to spot coronavirus infected people is more reliable when scanning the eyeball and fingertip than measuring body or forehead.
Experts in human physiology published a scientific paper on the usefulness of thermometers that scan a person’s skin to detect a fever.
They say the current process is fundamentally flawed and produces a large number of false negatives, as well as some false positives, and also because not all people infected with the coronavirus get a fever.
By taking two measurements from specific locations on the body with adequate blood flow, a more reliable estimate can be made of the body’s actual core temperature and whether it is elevated due to fever, the researchers believe.
Fever is defined as a temperature greater than or equal to 100.4F (38 ° C) when noticed outside of a healthcare setting.
In healthcare settings, such as a hospital, a fever is technically defined as anything greater than or equal to 100.0F (37.8 ° C).
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Rather than using thermal technology on the forehead to measure body temperature, the researchers say adjusting the device to get temperatures from the fingertip and eye would be a quick fix that dramatically improves reliability (photo)
The use of temperature scanners as a screening mechanism in offices, restaurants and airports is unreliable and inaccurate, researchers say (stock photo)
Forehead scan thermometers have become ubiquitous as a way to detect fever, the most common symptom of coronavirus infection.
Rather than using thermal technology on the forehead to measure body temperature, the researchers say adjusting the device to get temperatures from the fingertip and eye would be a quick fix that dramatically improves reliability.
Professor Mike Tipton of the University of Portsmouth, co-author of the study published in the journal Experimental Physiology, highlights four major problems with today’s scanners.
Detecting elevated body temperature itself is an unreliable indicator of a coronavirus infection, as at least 11 percent of people with Covid-19 do not have a fever, they say.
This drops to less than half for people hospitalized with Covid.
The researchers also point out that if a person produces a high body temperature, it is not a guarantee that they have Covid-19, as it could be the result of another infection, the weather, recent exercise, or alcohol consumption. .
These external factors are more likely to affect temperature readings from the forehead than the fingertip and eyeball.
Professor Tipton told MailOnline: ‘If you feel hot because you have been exercising, or have gotten warm in a warm environment / by wearing too much clothing, or if you are flushed from drinking alcohol, your forehead and finger temperature both increase.
If you have a fever, your head will be warm and your hand will be cool. So we think the difference between the two sites is more sensitive to identifying fever than just measuring the forehead.
“The good news is that the same kit can be used to get the temperature from both locations – you just need some software to calculate the difference.”
In addition to fever symptoms, the non-contact infrared gadgets used do not provide an accurate measurement of ‘deep’ body temperature.
To properly measure a person’s internal body temperature, a catheter is the best possible technique, with rectal thermometers the second best substitute.
This, the researchers say, is impractical as a Covid-19 screening method because it is very invasive and time-consuming.
In addition, taking a single measurement is always fraught with reliability issues, and it would be better to take two measurements from different parts of the body, the new study states.
For example, using retinal temperatures in conjunction with fingertip measurements would be a more robust method, the scientists advise.
Professor Tipton said, “Using a surface temperature scanner to obtain a single surface temperature, usually the forehead, is an unreliable method of detecting the fever associated with Covid-19.
“Too many factors make measuring skin temperature a bad substitute for deep body temperature; Skin temperature can change independently of deep body temperature for several reasons.
Even if such a single measurement reliably displays deep body temperature, other things, such as exercise, can raise deep body temperature.
“The pandemic has had a devastating effect on all aspects of our lives worldwide, and unfortunately it is unlikely to be the last pandemic we will face.
“It is critical that we develop a method to measure whether someone has a fever that is accurate and fast.”
The researchers looked through the vast body of research now available on the symptoms of Covid-19 in patients and found that in a February 2020 study from China, fever was the most common symptom of 55,924 confirmed cases of Covid-19.
But one in ten did not have a fever, and people were contagiously different data before they got a fever. These individuals would therefore have a window where they would pass thermal screening while spreading the virus to others.
Infrared scanners are ineffective as a screening tool for Covid-19 and have done little to prevent the spread of the disease, experts previously said (file)
Forehead scan thermometers have become ubiquitous as a way to detect fever, the most common symptom of coronavirus infection
A recent study from MailOnline found that thermal scanning devices record temperatures up to 1.4 ° C (2.5 ° F) lower than recommended.
MailOnline tested seven thermometers and obtained measurements for the same healthy person ranging from 36.2 ° C to 37.6 ° C. The infrared measurements were furthest from the measurement considered by experts to be the most reliable.
A reading greater than or equal to 38 ° C (100.4F) is considered a fever when taken outside of a care setting, and a high temperature is listed by the NHS as one of the main symptoms of coronavirus.
In an opinion piece published in December, Dr. William Wright of Johns Hopkins University and Dr. Philip Mackowiak, professor emeritus of medicine at the University of Maryland, criticized the use of thermal screening and said the devices left people in a false sense of bring safety. ‘.
Dr. Mackowiak told MailOnline that the true measurement of body temperature can only be obtained through a highly invasive procedure, reserved exclusively for critically ill hospital patients, which involves inserting a thermometer into the pulmonary artery through a catheter.
He said a rectal thermometer was the next most accurate method, but its obvious practical limitations make it unsuitable for screening. He suggested that an oral reading is the most accurate option.
But again, it “wouldn’t be practical in mass screening applications, especially if you’re dealing with a highly contagious pathogen like Covid-19.”
Experts do not approve of the use of infrared thermometers for the forehead
Leading doctors have warned against using infrared thermometers that scan a person’s forehead to check for a coronavirus infection.
Such technology has been widely used by shops, restaurants and workplaces as a form of screening for signs of fever, one of the main symptoms of Covid-19.
But Dr. William Wright of Johns Hopkins University and Dr. Philip Mackowiak, emeritus, professor of medicine at the University of Maryland School of Medicine, have questioned their accuracy, and claims that the devices are an effective tool for spreading of Covid-19.
Measurements obtained with a non-contact infrared thermometer are affected by numerous human, environmental and equipment variables, all of which can affect their accuracy, reproducibility and relationship to the measurement closest to what might be termed ‘body temperature’ – the core temperature, or the temperature of the blood in the pulmonary vein, ”says Dr. Wright.
“The only way to reliably record core temperature is pulmonary artery catheterization, which is not safe or practical as a screening test.”