Limitations of infrared thermography make skin-surface temperature scans an unreliable COVID-19 detection tool

Used to generate a heat map of infrared radiation emitted by heat sources, such as body temperature, infrared thermography (IRT) scans have become the go-to for mass detection of illnesses such as COVID-19. The limitations of this technology are revealed in research findings recently published in the Journal of Medical Imaging.

Led by Dr Babak Shadgan, a researcher at the Vancouver Coastal Health Research Institute, the study concluded that IRT relies too heavily on detecting high fever, which is only one of several symptoms of an active and well-developed COVID-19 infection. Underlying health conditions, stress, pregnancy, certain medications, and other environmental factors, such as temperature and humidity, can also alter someone’s surface body temperature. He notes that this can result in a false positive or false negative IRT reading.

Shadgan’s research reviewed 17 published studies on the effectiveness of IRT screening at airports around the world between 2002 and 2021. He found that the noncontact thermometer’s ability to detect SARS, dengue fever, swine flu, Ebola, and COVID-19 varied significantly. However, Shadgan admits that until a better rapid, non-invasive, affordable detection method becomes available, IRT will likely continue to be part of the disease detection toolkit.

He suggests that IRT can continue to be used if there is no other option, but that its results should not be relied upon exclusively. IRT is only really effective at detecting individuals who are symptomatic with a high fever. It does not detect asymptomatic individuals or infected individuals with only a slight rise in body temperature.

IRT has sometimes been paired with pulse oximetry to improve disease detection, which uses a fingertip sensor to detect oxygen saturation in a person’s bloodstream. Oxygen levels below 95% are found among people with pneumonia—another symptom of a severe COVID-19 infection.

Core body temperature is also a more accurate indicator of a COVID-19 infection, notes Shadgan. The limitations of present screening tools do, however, pose a challenge. To address this, Shadgan is developing a novel biosensor to take COVID-19 disease detection further. The noninvasive, simple-to-use, accurate biosensing device could be used for regular and routine COVID-19 screening and early diagnosis. Individuals with underlying health conditions, such as heart or liver disease, immune deficiency, diabetes, or cancer, could use the biosensor on a regular basis to check if they have COVID-19 symptoms.

The study, “Review of the efficacy of infrared thermography for screening infectious diseases with applications to COVID-19,” is available at www.ncbi.nlm.nih.gov/pmc/articles/PMC7995646.