Study: Temperature Scanners of Limited Value in Detecting COVID-19

A new study published in Experimental Physiology suggests that taking temperature readings of a person’s fingertip and eye would give a significantly better and more reliable reading and help identify those with fever compared to a full body scan.

"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," said professor Mike Tipton, University of Portsmouth, in a press release.

The study discovered 4 key factors, including:

• Temperature alone is not a good indicator of disease, since not everyone who has the coronavirus disease 2019 (COVID-19) virus has a fever. Those who do, develop one after being admitted to a hospital.
• Measuring skin temperature does not give an accurate estimation of deep body temperature, as a direct measure of deep body temperature is impractical.
• A high temperature, even taken from deep body, does not necessarily mean a person has COVID-19.
• Taking 2 temperature measurements (1 of the finger and 1 of the eye) is likely to be a better and more reliable indicator of a fever-induced increase in deep body temperature.

"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,” Tipton said in a press release. “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 researchers found that a significant proportion of those with COVID-19 do not have a fever, and fewer than half of those admitted to the hospital with suspected COVID-19 had a fever. Although the majority of positive cases go on to develop a high temperature after being admitted to the hospital, they were infectious before their temperature soared, according to the study authors.

"We think we can improve the identification of the presence of fever using the same kit but looking at the difference between eye and finger temperature—it's not perfect, but it is potentially better and more reliable,” Tipton said in a press release.

A change in deep body temperature is a critical factor in diagnosing disease with as little as a 1-degree increase indicating a potential disease. The many methods of detecting deep body temperature are either expensive, invasive, or time-consuming to be widely used outside of the hospital setting, according to the study authors.

A previous study in 2005 that compared forehead temperatures with 3 different infrared thermometers gave different temperatures for 1000 people, ranging from 31 °C to 35.6 °C. The infrared thermometer measurements alone varied by as much as 2 °C. Another study found that more than 80% of 500 people tested using infrared gave a false negative result.

Such differences in skin temperature could be due to multiple reasons, including whether the individual has recently exercised, has an infection, sunburn, how close an individual stands to a scanner, and even blood pressure, according to the study.

REFERENCE

Temperature scanners of limited value in detecting COVID-19. EurekAlert! https://www.eurekalert.org/pub_releases/2021-01/tps-tso011421.php. Published January 14, 2021. January 15, 2021.