Core body temperature measurement accuracy

What is CORE Body temperature measurement accuracy ?

This short note presents CORE Body temperature measurement accuracy and related validation studies.

Brief introduction to Core Body Temperature measurement

core body temperature measurement accuracy

Core Body Temperature is a vital parameter for monitoring an individual’s health status and refers to the body’s organs’ temperature. It is directly correlated to physiological processes such as physical activity, circadian and ovulation rhythm, or various illnesses and sleeping disorders.

Before this technology, it was possible to monitor the core body temperature via invasive methods such as rectal thermometers or single-use ingestible pills.

CORE rendered core body temperature health monitoring, easy, reliable and non-invasive. Other commercially available devices can estimate body temperature via skin surface temperature. Due to the complexity of thermal regulation and the thermal influences from changing environmental conditions and physical activity, this estimate does not come close to CORE’s precision and reliability.

What about in-ear (tympanic) and oral thermometers?

These methods can provide accurate results during stable conditions like in a hospital bed. But these single-point measurements do not provide much information about the health history of the patient or about the evolution of the patient health prior to the single-point measurement. The continuous temperature signal of CORE allows for better measuring performance and health monitoring with direct access to the instantaneous core temperature but also the patient health history.

core body temperature measurement accuracy

patient monitoring

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Why evaluating core body temperature measurement accuracy ?

Core body temperature measurement accuracy

As a new technology, our team is often asked about the accuracy of CORE. Delivering the best technology on the market is greenTEG’s R&D target. Therefore, more than five years of research and development have been invested and various validation studies have been performed internally and externally from our team testing or joint projects with clinical researchers and medical institutions. This technology currently supports three sensing solutions based on your application needs. The wearable core body temperature sensing solutions are described in details here.

This note gathers a set of independent studies completed or currently underway with sporting institutes, medical facilities and other research groups.

CORE uses a thermal energy transfer sensor (not skin temperature) and we validate against other ‘accurate’ methods, most commonly the ingested e-pill as this is best suited for sporting activity. CORE can now be sold as a clinical thermometer for use in the United States. For more in-depth information on the scientific data validation for cores accuracy, can be found here.

Core body temperature measurement accuracy

The clinical-grade accuracy according to ISO 80601-2-56:2017 has been validated by different hospitals and Universities.

OEM integration Wearables

External & Internal validation studies (wrist-worn, chest-worn and upper-arm validation studies) are available:

How to assess core body temperature measurement accuracy ?

First level of validation : Internal Testing

The accuracy and validation of core body temperature in various real-life conditions is continuousy improved thanks to a wide variety of participants who each have their own unique thermoregulation response.


To discover more about CORE body temperature accuracy for sport performance evaluation, click here. To learn more about our current public statement regarding Core body temperature measurement accuracy, click here.

Second level of validation : External Testing

External studies and projects

University of Trieste | A Novel Non-Invasive Thermometer for Continuous Core Body Temperature: Comparison with Tympanic Temperature in an Acute Stroke Clinical Setting

Ajčević, M., Buoite Stella, A., Furlanis, G., Caruso, P., Naccarato, M., Accardo, A., & Manganotti, P.

The CALERA® solution was validated with CORE in an independent clinical study led by Miloš Ajčević, Alex Stella and co-workers at the Cattinara University Hospital ASUGI in Trieste, Italy. The study was performed on 30 partially febrile stroke patients over 6 months.

The study showed a good agreement of the CORE with commonly used tympanic ear temperature measurements with no bias and a Limit of Agreement of: LoA 95% CI −0.55 – 0.77 °C. The CORE measured effectively and accurately fever which is crucial for early detection of the deterioration of stroke patients. The detection was performed correctly in 94% of the cases. Hyperthermia and fever were defined respectively for temperatures above 37.5°C and 38.3°C

In addition, the researchers compared greenTEG’s sensor to a forehead thermometer commonly employed for the observation of Stroke patients. The forehead thermometer shows a proportional bias of -0.388°C and a 95% LoA of−0.72 – 1.00 °C with a trend of an overestimation of lower temperatures and an underestimation of higher temperatures.

The following graph represents the accuracy (LoA) of the CALERA® solution determined for this specific study in comparison with other clinical thermometers.

Figure 1 Accuracy (LoA) comparison of the CALERA® solution determined for this specific study in comparison with other clinical thermometers.

The corresponding exact values and references are given in the Table 1 below:

Comparison of clinical thermometersBias (°C)95% LoA (°C)
Temporal Artery[1]0.380.86
Radiuse T°[4]0.170.96
Table 1

Innosuisse | A Virtual Wearable Sensor for Detection of Neurodegenerative Diseases
Giovanni Schiboni, Martin Rerabek, and Krzysztof Kryszczuk, ZHAW (Wädenswil); Philipp Eib, Fabien Rochat, Michele Zahner and Lukas Durrer, greenTEGAG (Zürich); Anneke Hertig-Godeschalk, David Schreier, Markus H. Schmidt, and JohannesMathis, Inselspital (Bern).

The thermal energy transfer sensor technology used in the CORE Body Temperature monitor is successfully being used in a Swiss based research project for early detection of Alzheimer and Parkinson diseases. Find out more here.

Abstract: Alzheimer (AD), and Parkinson Diseases (PD) are reported to manifest themselves in changes to the circadian rhythm. A novel virtual wearable wrist-worn sensor, deployable in free living conditions, enables long-term predictive monitoring of the core body temperature, which is the only health marker directly linked to the circadian rhythm. The goal is to distinguish between normal and pathological core body temperature trajectories.

Hochschule Luzern | Wearable Medical Device for Remote Monitoring the Health of Elderly People at Home
Diego Barrettino1), 2), Thomas Gisler1), Christoph Zumbühl1), Christian Di Battista1), Raphael Kummer1) and Markus Thalmann1) 1) Lucerne University of Applied Sciences and Arts (HSLU)

Abstract: The design, fabrication and testing of a wearable medical device for remote monitoring the health of elderly people at home are presented in this paper. The proposed wearable medical device comprises a wide range of sensors, innovative sensor fusion algorithms and flexible electrodes that make possible to continuously run analyses such as hydration assessment, stress assessment, body temperature assessment, fall detection and heart monitoring. In-vivo measurement results showed the excellent performance of this wearable medical device in real-life scenarios.

Inselspital | Universitäres Schlaf-Wach-Epilepsie-Zentrum SWEZ
Dr. Krzysztof Kryszczuk, ZHAW | ZHAW (@ZHAW) | Twitter

For this project completed in 2018, an early version of CORE was used at the INSEL hospital in a sleep study. Progress has been made since this study was published but even then the researchers were already satisfied with the results and could see the potential for this technology.
Visit Project Page:

Project: Non-invasive core body temperature sensor for wearable sleep monitoring devices. The objective of the project was to create a proof of concept that it is feasible to estimate the core body temperature from the wearable sensors using the skin temperature and heat flux sensors. In the course of the project, a prototype of a standalone wearable sensor device was developed. The sensor is lightweight and allows for non-invasive continuous estimation of Core Body Temperature with an average error smaller than 0.4 centigrade, using the measurements of the skin temperature and thermal energy transfer sensor.

Additional ongoing public projects

University Hospital Zurich
Fever algorithm development of a non-invasive wearable core body temperature sensor system in intensive care unit patients Identifier: NCT04182945

University Children’s Hospital Zurich
Development of a fever detection algorithm based on non-invasive skin-based sensor values in infants up to 18 months of age

BASEC Number: BASEC2019-02355


[1] Ajčević, Miloš, et al. “A Novel Non-Invasive Thermometer for Continuous Core Body Temperature: Comparison with Tympanic Temperature in an Acute Stroke Clinical Setting.” Sensors 22.13 (2022): 4760.

[2] Niven, Daniel J., et al. “Accuracy of peripheral thermometers for estimating temperature: a systematic review and meta-analysis.” Annals of internal medicine 163.10 (2015): 768-777.