Coronavirus News: John Hopkins And University Of Maryland Scientists Say Non-Contact Infrared Thermometers Not Effective As COVID-19 Screeners
: Researchers from Johns Hopkins Medicine and the University of Maryland School of Medicine conclude in a perspective editorial that while a fever is one of the most common symptoms for individuals who get sick with COVID-19, taking one's temperature is a poor means of screening who is infected with the SARS-CoV-2 coronavirus that causes the disease, and more importantly, who might be contagious.
The study team describes why temperature screening, primarily done with a non-contact infrared thermometer (NCIT)does not work as an effective strategy for stemming the spread of COVID-19.
The study team’s findings were published in the peer reviewed journal: Open Forum Infectious Diseases, the online journal of the Infectious Diseases Society of America. https://academic.oup.com/ofid/advance-article/doi/10.1093/ofid/ofaa603/6032722
The study team are led by Dr William Wright, D.O., M.P.H., assistant professor of medicine at the Johns Hopkins University School of Medicine, and Philip Mackowiak, M.D., M.B.A., emeritus professor of medicine at the University of Maryland School of Medicine.
The U.S. Department of Health and Human Services and the U.S. Centers for Disease Control and Prevention in March 2020, 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 playing an integral role.
The guidelines stated that 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-health care settings and greater than or equal to 100.0 degrees Fahrenheit (37.8 degrees Celsius) for health care ones.
Importantly this is the first aspect of COVID-19 screening by temperature that Dr Wright and Dr Mackowiak question in their editorial.
Dr Wright told Thailand Medical News, "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' ie the core temperature, or the temperature of blood in the pulmonary vein.”
He added, "However, the only way to reliably take the core temperature requires catherization of the pulmonary artery, which is neither safe nor practical as a screening test."
In the published editorial Dr Wright and Dr Mackowiak provide statistics to show that NCIT fails as a screening test for SARS-CoV-2 infection.
D Wright said, "As of Feb. 23, 2020, more than 46,000 travelers were screened with NCITs at U.S. airports, and only one person was identified as having SARS-CoV-2. In a second example, CDC staff and U.S. customs officials screened approximately 268,000 travelers through April 21, 2020, finding only 14 people with the virus."
Interestingly from a November 2020 CDC report, Dr Wright and Dr Mackowiak provide further support for their concern about temperature scre
enings for COVID-19.
The U.S. CDC report, they say, states that among approximately 766,000 travelers 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.
Furthermore 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.
Unfortunately, temperature screening programs intended to identify SARS-CoV-2-infected persons are, at best, marginally effective, because nearly half of infected persons never develop a fever. https://pubmed.ncbi.nlm.nih.gov/32491919/
Also another problem with NCITs, Dr Wright says, is that they may give misleading readings throughout the course of a fever that make it difficult to determine when someone is actually feverish or not.
Dr Wright explains, "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. And during a fever drop, the opposite happens. So, basing a fever detection on NCIT measurements that measure heat radiating from the forehead may be totally off the mark."
Readings obtained with NCITs, which measure surface temperature (generally of the mid-forehead), are influenced by numerous human, environmental and equipment variables, all of which can affect their accuracy, reproducibility and relationship with core temperature. These include the subject’s age and gender and medications (especially antipyretic drugs) being taken. https://pubmed.ncbi.nlm.nih.gov/8011836/
Women have slightly higher temperatures than men, African-Americans slightly higher temperatures than Caucasians. https://jamanetwork.com/journals/jama/article-abstract/400116
In addition, temperature varies in a circadian fashion, with early morning (oral) temperatures lower on average by 1.0o F (0.56oC) than evening temperatures. Then there is the emissivity (the capacity to emit heat by radiation) of the surface being examined, which is influenced by a person’s complexion, the wearing of makeup and sweat. Environmental factors, such as subject-to-sensor distance and ambient temperature and humidity, also affect readings obtained with NCITs
Dr Wright and Dr Mackowiak conclude 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.
The scientists suggest among the strategies for improvement are:
-lowering the cutoff temperature used to identify symptomatic infected people, especially when screening those who are elderly or immunocompromised.
-group testing to enable real-time surveillance and monitoring of the virus in a more manageable situation.
-"smart" thermometers ie wearable thermometers paired with GPS devices such as smartphones
-monitoring sewage sludge for SARS-CoV-2.
The temperature screening for COVID-19 by NCITs protocol was actually introduced by China, where the SARS-CoV-2 first appeared and spread to cause havoc around the world and is also one of the many stupid and unproven things to manage the COVID-19 crisis that the rest of the world adopted from China.
In Thailand, a close ally of China, temperature screenings are widely used around the country using NCITs made in China (China made millions selling these stupid devices to countries around the world!). In most shopping malls and public places, stupid and uneducated security guards with no medical or health training can be seen clumsily monitoring the temperature of public, sometimes sleeping or worse having defective devices! Ironically COVID-19 testing for the general public is not easily available!
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