CORE Team Blog

CORE Accuracy

As a new technology, we are often asked by athletes, researchers and media about the accuracy of the CORE sensor. We spent six years in research and development ahead of the launch in 2020, many of the studies are from our testing or joint projects with clinical researchers and medical institutions.

There are a series of independent studies currently underway with sporting institutes, medical facilities and other research groups and as these become available, we will add them here.

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.

Internal Testing

We continue to work on CORE Accuracy and validation in various real-life conditions with a wide variety of participants who each have their own unique thermoregulation response.

In the following article we have documented our testing approach, data collection and validation for sports.

CORE Accuracy Validation Testing

In our internal testing we validate against other accurate testing methods such as e-pills and have provided an overview of this validation including a number of graphs.

External studies and projects

Heat flux systems for body core temperature assessment during exercise
Journal of Thermal Biology Volume 112, February 2023, 103480
Doi: 10.1016/j.jtherbio.2023.103480
Year: 2023
Author(s): Hein A.M. Daanen and Veerle Kohlen and Lennart P.J. Teunissen

For this peer reviewed study, an experiment was performed in which three commercially available heat flux systems (3 M, Medisim and Core) were compared to rectal temperature (Tre). The premise is that for core body temperature measurments, "esophageal and rectal thermometry are not practical as they are rated as uncomfortable by the users" while "several non-invasive alternatives have major drawbacks as well regarding validity, reliability and usability. Therefore, there is a need for Tc methods that are valid, but also easy to use and comfortable". This study compared three heat flux solutions and concludes "The Core systems is easy to use, but tends to overestimate body core temperatures."

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 CORE was validated 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 the CORE 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 CORE 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 thermometers Bias (°C) 95% LoA (°C)
Bladder[2] 0.003 0.12
Rectal[2] 0.1 0.31
Esophageal[2] 0.003 0.31
Oral[2] 0.02 0.265
Axillary[2] -0.6 1.01
Tympanic[1] -0.03 0.92
Temporal Artery[1] 0.38 0.86
SpotOn[3] 0.23 0.88
Radiuse T°[4] 0.17 0.96
CORE[1] 0.003 0.77

A Virtual Wearable Sensor for Detection of Neurodegenerative Diseases
Giovanni Schiboni, Martin Rerabek, and Krzysztof Kryszczuk, ZHAW (Wädenswil); PhilippEib, FabienRochat, 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.
View Datasheet (PDF 910 KB)

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)
View Datasheet (PDF 1.5 Mb)

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.


Universitäres Schlaf-Wach-Epilepsie-Zentrum SWEZ
Dr. Krzysztof Kryszczuk, ZHAW

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.

Project: Noninvasive 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.