Medical technologies, including commonly used diagnostic devices, have historically been validated primarily in populations with lighter skin tones. As a result, increasing evidence suggests that such devices may have limitations when used in individuals with darker skin tones. Pulse oximeters, for example, have been shown to display measurement inaccuracies in people with non-white skin, potentially leading to clinically important delays in patient care, particularly among ethnic minority populations in the United Kingdom.

Similar concerns are now emerging regarding the accuracy of non-invasive infrared thermometers. A recent retrospective study from the United States identified significant measurement error in temporal artery and forehead thermometers among individuals with black skin, compared to sublingual temperature measurements. Specifically, temporal temperature readings were found to be lower than oral temperatures by an average of -0.07°C in individuals with black skin, a discrepancy not observed in white individuals. This variation had clinical implications, as the odds of detecting fever using temporal thermometers were significantly reduced in black patients (odds ratio 0.54, p=0.02), whereas no such difference was observed in white patients (odds ratio 0.91, p=0.62).

With an estimated 1.3 billion people living in Africa and 4.7 billion in Asia, the potential for measurement bias in non-invasive thermometers to impact clinical outcomes on a global scale is a serious concern. India, with a population of approximately 1.4 billion in 2021, is a setting where non-invasive thermometers are routinely used in both clinical and community settings, including during pandemics and public health emergencies.

Despite the widespread use of temporal and tympanic infrared thermometers in India, prospective evidence evaluating their accuracy in individuals with darker skin—such as those in South Indian populations—is lacking. This highlights the need for a feasibility study to assess the potential measurement error in these devices when compared to the gold-standard sublingual temperature measurement in this context.

Sample size: 5000 individuals in total. We will recruit 20 individuals/day for 250 days over a one-year period. No power calculation is provided as this is a feasibility study.

Methodology:

1.    Patients and visitors to Kasturba Hospital, Manipal, Karnataka, India and associated outreach centers will be recruited to the study after obtaining consent. Demographic data like Age, gender, area, occupation will be recorded.

2.    The following body temperature measurements will be taken in the same order

a.    Lingual temperature (using Probe Digital Thermometer-GS-9055).

b.    Temporal skin temperature (using Infrared thermometer Romson jumper JPD-FR 300).

c.     Tympanic temperature (using Infrared thermometer Romson jumper JPD-FR 300).

d.    Digital thermo-hygrometer (using EXACTO Digital Thermo-Hygrometer) – A thermo hygrometer is used to determine the humidity, and it can measure room temperature and humidity at the same time.

3.    Ambient room temperature within 15 minutes of the last body temperature measurement.

4.    Disposable Thermometer covers for sublingual, tympanic and skin thermometer will be used separately for each subject participating in the study.