Body temperature scanner holds limited value in detecting Covid-19: study

A new study argues that taking temperature readings of a person’s fingertip and the eye can give a more efficient reading and may help better in identifying Covid-19 cases during fever checks at airports and hospitals.

The study, co-led by a human physiologist and an expert in temperature regulation, Professor Mike Tipton, is published in Experimental Physiology.

Professor Tipton, of the University of Portsmouth, said: “If scanners are not giving an accurate reading, we run the risk of falsely excluding people from places they may want or need, to go, and we also risk allowing people with the virus to spread the undetected infection they have.”

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The study noted that temperature alone is not a good indicator of disease — not all who have the virus have a fever and many who do, develop one only after admission to hospital.

It also stated that measuring skin temperature doesn’t give an accurate estimation of deep body temperature (raised in a fever). A direct measure of deep body temperature is impractical.

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The researchers mentioned that the high temperature, even one taken from the deep body, does not necessarily mean a person has Covid-19. A significant proportion (at least 11 per cent) of those with Covid-19 infection does not demonstrate fever as a symptom.

Also, taking two temperature measurements, one of the finger, the other of the eye, is likely to be a better and more reliable indicator of a fever-induced increase in deep body temperature.

Variation

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,” he added.

The researchers mentioned a previous study that had been carried out in 2005 and involved 1,000 people. The study had compared the forehead temperature of the participants with three different infrared thermometers that gave different temperatures. That ranged from 31 °C to 35.6 °C.

The infrared thermometers measurements alone varied by as much as 2 °C. In another study, more than 80 per cent of the 500 people tested using infrared gave a false negative result.