Significance: Infrared thermographs (IRTs) have been used for fever screening during infectious disease epidemics, including severe acute respiratory syndrome, Ebola virus disease, and coronavirus disease 2019 (COVID-19). Although IRTs have significant potential for human body temperature measurement, the literature indicates inconsistent diagnostic performance, possibly due to wide variations in implemented methodology. A standardized method for IRT fever screening was recently published, but there is a lack of clinical data demonstrating its impact on IRT performance.
Aim: Perform a clinical study to assess the diagnostic effectiveness of standardized IRT-based fever screening and evaluate the effect of facial measurement location.
Approach: We performed a clinical study of 596 subjects. Temperatures from 17 facial locations were extracted from thermal images and compared with oral thermometry. Statistical analyses included calculation of receiver operating characteristic (ROC) curves and area under the curve (AUC) values for detection of febrile subjects.
Results: Pearson correlation coefficients for IRT-based and reference (oral) temperatures were found to vary strongly with measurement location. Approaches based on maximum temperatures in either inner canthi or full-face regions indicated stronger discrimination ability than maximum forehead temperature (AUC values of 0.95 to 0.97 versus 0.86 to 0.87, respectively) and other specific facial locations. These values are markedly better than the vast majority of results found in prior human studies of IRT-based fever screening.
Conclusion: Our findings provide clinical confirmation of the utility of consensus approaches for fever screening, including the use of inner canthi temperatures, while also indicating that full-face maximum temperatures may provide an effective alternate approach.
Infrared thermography (IRT) – a non-contact, non-invasive technique – has been used for mass screenings to identify febrile individuals at transportation nodes (e.g., airports) during infectious disease pandemics such as SARS (Severe Acute Respiratory Syndrome), H1N1 virus, and Ebola outbreaks. Despite the potential of IRTs, the field lacks a well-established consensus methodology to ensure temperature measurement accuracy and reliability. This study aims to investigate the use of IRTs in a controlled setting to determine the effectiveness of IRT and the most reliable facial region for estimation of core temperature. We conducted a large clinical study, acquiring facial thermographs of 1,109 febrile and non-febrile subjects using Screening Thermographs (STs). Regression analyses between the reference oral temperature and different areas of the face, specifically the forehead and canthi, were carried out. The coefficients of determination of each regression were compared to determine how well facial and core body temperatures were correlated. Receiver operating characteristic (ROC) curves were constructed to compare the effectiveness of using different facial areas to identify febrile patients. Results show that the maximum temperature of the overall face has the best linear trend, followed by the maximum temperature at the inner canthus region. Both of these values show better correlations than forehead temperatures, which are commonly used as a target by non-contact infrared thermometers. For any chosen facial area, the maximum temperature collected always showed a stronger correlation than a specific point in that area. Results indicate that IRT performance is substantially approved when applying optimal measurement methodology.
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