Thermal screening to spot people infected with coronavirus is more reliable when scanning the eyeball and fingertip than taking body or forehead measurements.
Experts in human physiology published a scientific article on the usefulness of thermometers which 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 develop a fever.
Taking two measurements from specific locations on the body with ample blood flow allows for a more reliable estimate of the true core body temperature and if it is elevated due to fever, the researchers believe.
A fever is defined as a temperature of greater than or equal to 100.4F (38°C) if spotted outside of a healthcare environment.
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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Instead of using thermal technology on the forehead to gauge body temperature, the researchers say adapting the apparatus to get temperatures from the fingertip and eye would be a quick fix that has drastic improvements to reliability (pictured)
Using temperature scanners as a screening mechanism in offices, restaurants and at airports is unreliable and inaccurate, researchers have stated (stock photo)
Forehead-scanning thermometers have become ubiquitous as a way of detecting a fever, the most common symptom of coronavirus infection.
Instead of using thermal technology on the forehead to gauge body temperature, the researchers say adapting the apparatus to get temperatures from the fingertip and eye would be a quick fix that has drastic improvements to reliability.
Professor Mike Tipton from the University of Portsmouth, co-author of the research published in the journal Experimental Physiology, points to four major issues with the current scanners.
Detecting an elevated body temperature itself is an unreliable indicator of coronavirus infection, as at least 11 per cent of those with Covid-19 do not have a fever, they say.
This drops to less than half for people with Covid admitted to hospital.
Also, the researchers point out, if a person does produce a high body temperature, this is not a guarantee they have Covid-19, as it could be the result of another infection, the weather, recent exertion or consumption of alcohol, for example.
These external factors are more likely to affect temperature measurements from the forehead compared to the fingertip and eyeball.
Professor Tipton told MailOnline: ‘If you are hot due to having exercised, or got warm in a hot environment/by wearing too many clothes, or flushed due to having consumed alcohol, your forehead temperature and finger temperature will both be increased.
‘If you have a fever your head will be hot and your hand cool. So, we think the difference between the two sites is more sensitive to identifying a fever than just measuring the forehead.
‘The good news is that the same kit can be used to get the temperature from both sites – you just need a bit of software to calculate the difference.’
As well issues with the fever as a symptom, the non-contact infrared gadgets being employed also do not give an accurate measure of ‘deep’ body temperature.
To get a true gauge of a person’s internal body temperature a catheter is the best possible technique, with rectal thermometers the next best substitute.
This, the researchers say, is impractical as a Covid-19 screening method as it is highly-invasive and time-consuming.
Also, taking a single measurement is always fraught with reliability issues, and taking two measurements from different parts of the body would instead be better, the new study states.
For example, using retinal temperatures in conjunction with measurements taken from the fingertip would be a more robust method, the academics advise.
Professor Tipton said: ‘Using a surface temperature scanner to obtain a single surface temperature, usually the forehead, is an unreliable method to detect the fever associated with Covid-19.
‘Too many factors make the measurement of a skin temperature a poor surrogate for deep body temperature; skin temperature can change independently of deep body temperature for lots of reasons.
‘Even if such a single measure did reflect deep body temperature reliably, other things, such as exercise can raise deep body temperature.
‘The pandemic has had a devastating global effect on all aspects of our lives, and unfortunately, it’s unlikely to be the last pandemic we face.
‘It’s critical we develop a method of gauging if an individual has a fever that’s accurate and fast.’
The researchers looked through the vast reems 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 Covid-19 cases.
But one in ten did not have a fever and people were infectious several data before they developed 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 very little to prevent the spread of the disease, experts said previously (file)
Forehead-scanning thermometers have become ubiquitous as a way of detecting a fever, the most common symptom of coronavirus infection
A recent MailOnline investigation found thermal-scanning devices registering temperatures up to 1.4°C (2.5°F) lower than recommended methods.
MailOnline tested seven thermometers and obtained readings for the same healthy person which ranged from 36.2°C to 37.6°C. The infrared readings were the farthest from the measure considered most reliable by experts.
A reading greater than or equal to 38°C (100.4F) is considered a fever when taken outside of a healthcare environment, and a high temperature is cited by the NHS as one of the main symptoms of coronavirus.
In an opinion piece published in December, Dr William Wright at the Johns Hopkins University and Dr Philip Mackowiak, Emeritus professor of medicine at the University of Maryland, criticised the use of thermal screening and said the devices ‘lull people into a false sense of security’.
Dr Mackowiak told MailOnline the true reading for body temperature can only be obtained via a highly invasive procedure, reserved solely for seriously ill hospital patients, which inserts a thermometer into the pulmonary artery via 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 an oral reading is the most accurate option.
But, again, it ‘would not be practical in massive screening applications, especially when you’re concerned with a highly infectious pathogen such as Covid-19’.
Experts slam the use of infrared forehead-scanning thermometers
Leading doctors have warned against the use of infrared thermometers that scan a person’s forehead to check for coronavirus infection.
Such technology was widely deployed by shops, restaurants and workplaces as a form of screening to spot signs of fever, one of the main symptoms of Covid-19.
But Dr William Wright at the Johns Hopkins University and Dr Philip Mackowiak, Emeritus, professor of medicine at the University of Maryland School of Medicine, have questioned their accuracy, and rubbished claims the devices are an effective tool in preventing the spread of Covid-19.
‘Readings obtained with non-contact infrared thermometer are influenced by numerous human, environmental and equipment variables, all of which can affect their accuracy, reproducibility and relationship with the measure closest to what could be called the “body temperature” – the core temperature, or the temperature of blood in the pulmonary vein,’ says Dr Wright.
‘However, the only way to reliably take the core temperature requires catheterisation of the pulmonary artery, which is neither safe nor practical as a screening test.’