Data accuracy validation for CORE - How it works?

A common question we get from coaches is how CORE works, as well as its accuracy. We have introduced this here, and can expand on this. The CORE sensor is a wearing monitoring solution that is very accurate but like all equipment it is useful to understand how it works and how it is validated so that it can be used appropriately and successfully.

Core body temperature monitoring solutions in context

First, we would like to provide some context about core body temperature monitoring solutions that will help to understand our product better, as well as why CORE is so unique.

Up to now, core body temperature monitoring solutions were either invasive, not accurate, or non- continuous. Thermometers can monitor the temperature inside the body (not only skin surface temperature), but there is always a deviation, and no thermometer could feasible monitor for more than a few minutes.

To try solving this lack of continuous monitoring, there have been have two solutions: electronic pills and probes.

Electronic pills (e-pills) are small pills than contain a battery and electronics which you swallow to monitor the temperature inside your body. These are considered accurate and continuous though the monitoring is limited to the time that the pill takes to go from the entrance to the exit. The recorded temperature also varies as it passes through the body because your body’s temperature is not homogeneous, a tolerance that is regarded as acceptable and different brands can deliver varying results. E-pills cost between 50 - 80 Euro each and require additional reusable hardware (activator and reader which cost 1000-2000 euros). The electronic pills are used extensively by researchers and select testing with elite athletes.

The alternative is the internal probe, i.e. rectal thermometer. This is typically for medical use and there can be variations in reading depending how the test is conducted. Some rectal thermometers take a single temperature reading while others can capture continuous readings. For sports training this is a quite invasive method and only occasionally employed although for heat-stroke and when medical attention is required this is the standard approach used by trained professionals to capture medically accurate data.

CORE offers an alternative that is both continuous and non-invasive. It predicts the core body temperature using a miniaturized energy transfer sensor, combined with a machine learning algorithm that crunches the data to deliver a continuous stream of core body temperature data. CORE is non-invasive, and has a battery that could last 6 days (more than enough for all the applications).

But is it as accurate as the e-pill and internal probe? CORE uses these two approaches to validate the data (and also continually optimise) and our clinical, lab and field tests show that we provide medical grade accuracy and for the conditions against which CORE is validated, provide a high level of accuracy within the tolerance of e-pills and internal probs.

Validating CORE with e-pills in different sports scenarios.

As documented here, we have extensively tested CORE with a rigid protocol, involving professional athletes. We asked them to wear CORE while training and competing both indoors and outdoors, monitoring their core body temperature before, during, and after the workout. Simultaneously the athletes used a reference thermometer. Predominantly electronic pills were used as these are usually more appropriate for sports.

As a result, the CORE Body Temperature Monitoring technology has a really good accuracy compared to invasive thermometers, as shown in the following charts for 'everyday living' activity and endurance sports activity.

Graph comparing the e-pill and CORE during an indoor cycling session (wintertime), temperate indoor conditions (24°C, 35% RH).

Graph comparing the e-pill and CORE during an indoor cycling session (wintertime), temperate indoor conditions (24°C, 35% RH).

Graph comparing the e-pill and CORE during an outdoor cycling session during wintertime. Mountain ride, temperate conditions between 10-15 °C.

Graph comparing the e-pill and CORE during indoor cycling, moderate intensitiy in hot, dry room (33°C, 40% RH)

The data validation confirms that the CORE, as a wearable thermometer can be compared with electronic pills in accuracy and has an appropiate level of tolerance.

Validating CORE for medical purposes

CORE is not a medical device. However, we are also testing it for medical purposes and for many years have been working with partners in the field in a number of clinical studies. The ability to employ a non-invasive but accurate thermometer that provides real-time core body temperature data is extremely attractive within the medical profession. Our objective is to continue to improve the accuracy and validation for medical use and to gain formal medical approval. Currently the CORE device is only for sale and use under the FDA`s Emergency Use Authorization provisions (EUA) linked to the COVID-19 requirements to support this current public health emergency. 

For medical testing with CORE, the measurements are performed by qualified healthcare professionals and compared with other methods for data validation. Below, are some charts showing results from recent studies.

Graph comparing the e-pill and CORE during fever event in clinical setting (indoor, temperate conditions).

These tests show that CORE monitors fever in real time with accuracy. Today, our accuracy has Mean Absolute Deviation of 0.21 °C, which is similar to the accuracy of the e-pill.

As a new technology we have made excellent gains in accuracy and as we continue to gather data and test and validate CORE for specific condition, this will enable use to continue to improve our accuracy. While this means that we recognise that there are some conditions where further improvements are needed, our pilot programs and ongoing testing allow use to feed the results back into our algorithm and then continually provide CORE customers with updates.

If you have specific tests or requirements for monitoring core body temperature, please talk to us and we can help guide you on the suitability of CORE for your specific needs.