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Thermal Screening in COVID-19: Why Is It Commonplace?

Published:October 01, 2021DOI:https://doi.org/10.1016/j.mayocp.2021.09.018
      To the Editor:
      Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, disrupted human life as we know it and brought us to a standstill in a matter of months. Considering fever is one of the earliest and most common symptoms, temperature-based screening promptly became the focus for identifying infected cases and for checking the spread of the virus.
      • Wang Z.
      • Yang B.
      • Li Q.
      • Wen L.
      • Zhang R.
      Clinical features of 69 cases with coronavirus disease 2019 in Wuhan, China.
      This was, and still is, being performed using noncontact infrared thermometers and/or thermal scanners at entry/exit points (eg, airports) and doorways to different establishments such as hospitals, workplaces, grocery stores, and restaurants. This was meant to be applied as part of a composite program in combination with self-reporting of relevant symptoms, contact, and travel history. The idea was that people who have a rise in body temperature be treated as a suspected case of COVID-19 and be isolated until definite test results are obtained.
      Per contra, what seemed like a simple yet effective measure to identify cases then has now transpired to be a futile endeavor. More than a year into the pandemic, we now know that almost half the patients with COVID-19 do not have fever.
      • Oran D.P.
      • Topol E.J.
      Prevalence of asymptomatic SARS-CoV-2 infection.
      Consequently, asymptomatic and presymptomatic cases might go undetected. Among cases that present with fever, the use of antipyretic drugs (which is oftentimes not self-reported) can result in false-negative results. Furthermore, readings obtained with these devices are influenced by a myriad of factors. These include the person’s age, sex and race, alcohol consumption, application of cosmetics, and physical activity preceding measurement. Environmental factors such as subject-to-sensor distance, ambient temperature, and humidity also affect the readings.
      • Wright W.F.
      • Mackowiak P.A.
      Why temperature screening for coronavirus disease 2019 with noncontact infrared thermometers does not work.
      Such factors may lead to an underestimation of febrile cases, leading to a false sense of security; conversely, it may also overestimate the number of febrile patients generating unnecessary further testing, increased cost, and undue stress for individuals and authorities involved.
      • Cardwell K.
      • Jordan K.
      • Byrne P.
      • et al.
      The effectiveness of non-contact thermal screening as a means of identifying cases of Covid-19: a rapid review of the evidence.
      Nowadays, temperature checks have come to be a daily ritual for many of us. Although not particularly resource intensive, the propensity to miss a substantial proportion of the cases and the multitude of variables that could render the results unreliable compel us to consider the cost-benefit of this screening measure. A review of the evidence of noncontact thermal screening for identifying cases of COVID-19 concluded that thermal screening is ineffective in limiting the spread of severe acute respiratory syndrome coronavirus 2.
      • Cardwell K.
      • Jordan K.
      • Byrne P.
      • et al.
      The effectiveness of non-contact thermal screening as a means of identifying cases of Covid-19: a rapid review of the evidence.
      With little discernible benefit, it begs the question: Why do we allow thermal screening to be commonplace?

      References

        • Wang Z.
        • Yang B.
        • Li Q.
        • Wen L.
        • Zhang R.
        Clinical features of 69 cases with coronavirus disease 2019 in Wuhan, China.
        Clin Infect Dis. 2020; 71: 769-777
        • Oran D.P.
        • Topol E.J.
        Prevalence of asymptomatic SARS-CoV-2 infection.
        Ann Intern Med. 2020; 173: 362-367
        • Wright W.F.
        • Mackowiak P.A.
        Why temperature screening for coronavirus disease 2019 with noncontact infrared thermometers does not work.
        Open Forum Infect Dis. 2021; 8: ofaa603
        • Cardwell K.
        • Jordan K.
        • Byrne P.
        • et al.
        The effectiveness of non-contact thermal screening as a means of identifying cases of Covid-19: a rapid review of the evidence.
        Rev Med Virol. 2021; 31e2192