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Biosecurity News in Brief
Study Finds that Rapid Tools for Measuring Fever are Not Reliable for Screening for InfectionBy Jennifer Nuzzo, July 28, 2008 According to a new study in the journal Emerging Infectious Diseases, infrared thermal devices, which measure the temperature of an individual’s skin, are poor predictors of whether or not that individual has a fever. The results of the study suggest that such devices, which have been proposed for screening individuals for infection in airports and hospital entries, may not be effective.1 The study notes that “recent efforts to control spread of epidemic infectious diseases have prompted health officials to develop rapid screening processes” to detect whether individuals entering airports or hospitals have a fever.1 Such tools assume that fever, which is thought to be a measure of whether or not an individual is infectious, can be rapidly assessed by measuring skin temperature. However, little is known about the accuracy of skin temperature-based scanning devices in correctly identifying infectious individuals. To test the accuracy of rapid screening devices in measuring fever, the authors investigated the correlation between the skin temperatures and fever (as measured by core body temperature) among 2026 patients in an emergency department of a large academic hospital (1,800 beds).1 The investigators measured skin temperature using a hand-held infrared thermometry device and compared skin temperatures with core body temperatures that were taken with an in-ear device (which has been established as “an appropriate measure of core temperature” in the medical literature).1 The study was not designed to test the accuracy of the infrared device; it was designed to test whether rapid measurement of skin temperature is an accurate detector of fever. According to the study, while the infrared tool correctly ruled out fever among 99% of individuals who did not have fever according to their core-temperature measurement, it correctly identified fever in only 10% of patients. Moreover, the authors found that the accuracy of skin-temperature-based devices varied with regard to the degree of an individual’s fever, outdoor temperature, and age of the patient. Consequently, the authors concluded that measuring a patient’s skin temperature with an infrared device does not reliably detect fever.1 Although the study only specifically investigated the performance of simple infrared thermometry, the authors note that it “should not be considered a limitation” of the study.1 Rather, they maintain that study results suggest that skin temperature is a poor predictor of core body temperature. These findings call into question the accuracy of any technology that attempts to assess fever by measuring skin temperature (including “sophisticated imaging” techniques, such as the large thermal scanners that are deployed in some international airports).1 The study also points out that, in addition to the lack of correlation between skin temperature and fever, there are other biological reasons why rapid methods of screening for fever are poor predictors of disease. Specifically, 1) “fever is not a constant phenomenon during an infectious disease”; 2) infection may actually reduce the core body temperature of some individuals; and 3) medications that individuals commonly take when they are ill may reduce fever.1 Consequently, the authors conclude that rapid tools for measuring skin temperature do not provide a “reliable basis for screening” for infectious diseases.1 References
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