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Non-contact infrared thermometers miss 5 out of 6 fevers

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By Dr. Joaquin Azpilicueta of Exergen Corporation.

Though the SARS, MERS and Ebola outbreaks each resulted in loss of life, they were restricted to a relatively small number of countries. COVID-19 has proved far more challenging to contain. No part of the world has managed to avoid the virus and its impact, making it the most significant global pandemic in over a century.

As it makes its resurgence and continues to spread across the globe, establishments such as businesses, hospitals, transportation systems, and community organisations are working on developing plans to one day, resume normal or phased operations.  These plans may include an initial assessment to try to identify people who may be infectious to limit the spread of infections.

Temperature measurement can be one part of the assessment to determine if a person has an elevated temperature potentially caused by a COVID-19 infection so understanding the difference in accuracy between temporal artery thermometers (TAT) and non-contact devices – now used widely for public temperature screenings – is of paramount importance.

Body temperature represents the balance between heat production and heat loss. If the rate of heat generated equates to the rate of heat lost, the core body temperature will be stable. All metabolising body cells manufacture heat in varying amounts. Therefore, body temperature is not evenly distributed across the body.  Core body temperature is found in the blood supplying organs such as the brain and those in the abdominal and thoracic cavities. Temporal thermometers take advantage of the temporal artery’s location as it is an easily accessible artery with constant blood flow. This combination, along with the arteries’ shallow depth from the skin surface, provides the scanner a clinically accurate and non-invasive way of taking a temperature measurement.

During the current COVID-19 pandemic a large majority of public temperature measurements are being performed using non-contact thermometers. A new study published in the American Journal of Infection Control shows that in many cases these NCIT thermometers are not accurate enough and may even produce a false sense of security.

The study is called ‘Comparative accuracy testing of non-contact infrared thermometers and temporal artery thermometers in an adult hospital setting’. The study is the result of research by scientists Shahrukh Khan (PhD), Bridey Saultry, Scott Adams (PhD), Abbas Z. Kouzani (PhD), Kelly Decker (MN), Robin Digby (PhD) and Tracey Bucknall (PhD) of Deakin University, Geelong, Australia.

In their study they conclude: ‘This is the first study to compare accuracy of NCIT thermometers to TAT in adult patients. Although mass fever screening is currently underway using NCIT, these results indicate that the NCIT may not be the most accurate device for fever mass screening during a pandemic’.

Non-contact infrared thermometers – often called ‘IR guns’ or ‘infrared guns’ – are non-invasive thermometers for fever screening. Until recently there was no evidence of their accuracy for fever screening in adults. The now published Australian study is the first to do so. And the results of this study have serious ramifications for public health and family safety.

The results are as follows. In 265 patients at two hospitals, a mean difference of ± 0.26°C was recorded between the NCIT (36.64°C) and the reference TAT (36.90°C) temperature devices. Bland-Altman analysis showed that NCIT and TAT temperatures were closely aligned at temperatures <37.5°C, but not at temperatures >37.5°C. NCIT had low sensitivity (16.13%) at temperatures ≥37.5°C. An AUROC score of 0.67 (SD 0.05) demonstrated poor accuracy of the NCIT device at temperatures ≥37.5°C. In other words, at fever levels NCIT devices perform significantly less accurate compared to the reference temporal artery thermometer.

The results of the study show that the non-contact infrared thermometers missed 5 out of 6 fevers. At the same time doctors and nurses around the world are fully aware of the fact that even during an unpredictable and escalating pandemic like the current COVID-19 situation there is just one constant in helping too ensure public safety: the ability to accurately screen for fever.

To be able to do so public health officers in many countries rely on non-contact infrared thermometers of which many suspected they were not accurate enough. The Australian study published in the American Journal of Infection Control now proves that ‘infra red guns’ or ‘IR guns’ are not the best devices to screen for fever. With over 80 peer-reviewed study temporal artery thermometers are much better suited for public screenings because of their much better performance when it comes to accuracy and detecting fevers.

This evidence is critical in helping clinicians and organisations involved in temperature screening protect the people they care for and the workforce Healthcare professionals must use the most accurate and precise measurement devices available if they are going to have a chance in the fight against the pandemic.

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