Validity of the Use of Wrist and Forehead Temperatures in Screening the General Population for COVID-19: A Prospective Real-World Study

We aimed to compare the accuracy of individuals’ wrist and forehead temperatures with their tympanic temperature under different circumstances.

We performed a prospective observational study in a real-life population in Ningbo First Hospital in China. We consecutively recorded individuals’ wrist and forehead temperatures in Celsius (°C) using a noncontact infrared thermometer (NCIT). We also measured individuals’ tympanic temperature using a tympanic thermometer (IRTT) and defined fever as a tympanic temperature of ≥37.3 °C.

We enrolled 528 participants, including 261 indoor and 267 outdoor participants. We grouped the outdoor participants into four groups according to their means of transportation to the hospital: by foot, by bicycle/electric vehicle, by car, or as a passenger in a car. Under different circumstances, the mean difference in the forehead measurement ranged from -1.72 to -0.56 °C across groups, and that in the wrist measurement ranged from -0.96 to -0.61°C. Both measurements had high fever screening abilities in indoor patients. (Wrist: AUC 0.790; 95% CI: 0.725-0.854, P<0.001; forehead: AUC 0.816; 95% CI: 0.757-0.876, P <0.001). The cut-off value of the wrist measurement for detecting a tympanic temperature of ≥37.3 °C was 36.2 °C, with 86.4% sensitivity and 67.0% specificity, and the best threshold for the forehead measurement was 36.2 °C, with 93.2% sensitivity and 60.0% specificity.

Wrist measurements are more stable than forehead measurements under different circumstances. Both measurements have favorable fever screening abilities in indoor patients. The cut-off values were both 36.2 °C.