New study says non-contact infrared thermometers are not successful as Covid-19 screeners

BALTIMORE: One of the most

common symptoms

of Covid-19 is being sick with fever, whereas a study by

Johns Hopkins Medicine

and

the University of Maryland School of Medicine

describes that

temperature screening

, primarily done with a non-contact infrared thermometer (NCIT) is not an effective strategy to staunch the spread of Covid-19 virus.


According to an editorial published in Open Forum Infectious Diseases, the online journal of the Infectious Diseases Society of America, the first aspect of Covid-19 screening by the temperature that the researchers questioned was when the US Department of Health and Human Services and the US.

Centres for Disease Control and Prevention

released guidelines for Americans to determine if they needed to seek medical attention for symptoms suggestive of infection with SARS-CoV-2, with temperature screening.

According to the guidelines, fever is defined as a temperature taken with an NCIT near the forehead -- of greater than or equal to 100.4 degrees Fahrenheit (38.0 degrees Celsius) for non-healthcare settings and greater than or equal to 100.0 degrees Fahrenheit (37.8 degrees Celsius) for health care ones.

An author of the study, William Wright said, "Readings obtained with NCITs 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' or the core temperature, or the temperature of blood in the pulmonary vein."

"However, the only way to reliably take the core temperature requires catheterization of the pulmonary artery, which is neither safe nor practical as a screening test," he said.

In their editorial, Wright and Mackowiak provided statistics to show that NCIT fails as a screening test for SARS-CoV-2 infection.

"As of Feb. 23, 2020, more than 46,000 travellers were screened with NCITs at US airports, and only one person was identified as having SARS-CoV-2," told Wright.

From a November 2020 CDC report, Wright with his fellow co-author Philip Mackowiak provided further support for their concern about temperature screenings for Covid-19. The report, they said, stated that among approximately 766,000 travellers screened during the period Jan. 17 to Sept. 13, 2020, only one person per 85,000 -- or about 0.001% -- later tested positive for SARS-CoV-2. Additionally, only 47 out of 278 people (17%) in that group with symptoms similar to SARS-CoV-2 had a measured temperature meeting the CDC criteria for fever.

Another problem with NCITs, Wright said, is that they may give misleading readings throughout the course of a fever that makes it difficult to determine when someone is actually feverish or not.

"During the period when a fever is rising, a rise in core temperature occurs that causes blood vessels near the skin's surface to constrict and reduce the amount of heat they release," Wright explained. "And during a fever drop, the opposite happens. So, basing fever detection on NCIT measurements that measure the heat radiating from the forehead may be totally off the mark," he added.

Wright and Mackowiak concluded their editorial by saying that these and other factors affecting thermal screening with NCITs must be addressed to develop better programs for distinguishing people infected with SARS-CoV-2 from those who are not.

Concluding the editorial, they also suggested strategies for improvement like, (1) lowering the cutoff temperature used to identify symptomatic infected people, especially when screening those who are elderly or immunocompromised, (2) group testing to enable real-time surveillance and monitoring of the virus in a more manageable situation, (3) 'smart' thermometers i.e.wearable thermometers paired with GPS devices such as smartphones, and (4) monitoring sewage sludge for SARS-CoV-2.