Validation Study
The accuracy is dependent on the use-case and on the reference thermometer method used. CALERA uses ingested electronic pills as the primary reference which is a widely accepted solution for measuring accurate core body temperature.
The following charts shows the accuracy of different thermometer types by Casa et al. [1], as well as the CORE sensor data from the Verdel et al. [2] study and greenTEG`s internal study. All datapoints are recorded during sports using a rectal thermometer as the reference method with the exception of greenTEG`s internal validation which uses ingested electronic pills.
Casa et al defined an accuracy threshold for the bias of maximum 0.27° C. All studies with CORE showed that CORE/CALERA Research is well within this limit. greenTEG`s internal studies found a bias of 0.03 ° C. and Verdel et al. found a bias of -0.10 & 0.23 depending on the activity level.
The bias explains how precise a method is, meaning that the average of all measurements is close to the true measurement, but the spread of the error can still be large. A better indication of the accuracy is the 95 % Limit of Agreement. This value shows you that 95% of all measurement fall within this range from the bias. In the next chart we show different thermometer types with respect to Limits of Agreement, and also include the CORE sensor data from the Verdel et al. study and greenTEG`s internal study. Again, all points follow from measurements during sports and use a rectal thermometer as a reference, except our internal validation which uses gastrointestinal pills.
Casa et al. Does not present a cut-off value for the limits of agreement, but Mogensen et al. [3] found that the limit of agreement from one of the best aurial (in-ear) thermometer used in a medical environment is 0.8° C. All values below this line should be considered highly accurate. Based on the data available, both from us and Verdel et al., CORE should be considered the most accurate non-invasive method for core body temperature measurements. (greenTEG = 0.56° C, Verdel et al. 0.55 ° C & 0.61 ° C)
Feel free to contact us and discuss your study and the implications your use-case has on the accuracy.
Thermometer methods
As your core temperature is not uniformly distributed in your body, various thermometer methods react differently to external and internal thermal influences. It is therefore important to always keep the thermometer method in mind when reading about study results. As CALERA Research’s algorithm is mainly based on ingestible pill data it will also behave most similar to this method. Have a look in the papers below where the differences between these methods are discussed.
Esophageal vs. rectal probe vs. telemetric pill
Esophageal vs. rectal probe
Rectal probe vs. telemetric pill
Rectal probe vs. Tympanic temperature
References
[1] Casa DJ, Becker SM, Ganio MS, Brown CM, Yeargin SW, Roti MW, Siegler J, Blowers JA, Glaviano NR, Huggins RA, Armstrong LE, Maresh CM. Validity of devices that assess body temperature during outdoor exercise in the heat. J Athl Train. 2007 Jul-Sep;42(3):333-42. PMID: 18059987; PMCID: PMC1978469.
[2] Verdel, N.; Podlogar, T.; Ciuha, U.; Holmberg, H.-C.; Debevec, T.; Supej, M. Reliability and Validity of the CORE Sensor to Assess Core Body Temperature during Cycling Exercise. Sensors 2021, 21, 5932. https://doi.org/10.3390/s21175932
[3] Mogensen CB, Vilhelmsen MB, Jepsen J, Boye LK, Persson MH, Skyum F. Ear measurement of temperature is only useful for screening for fever in an adult emergency department. BMC Emerg Med. 2018 Dec 3;18(1):51. doi: 10.1186/s12873-018-0202-5. PMID: 30509206; PMCID: PMC6276133.
[4] Gosselin, J.; Béliveau, J.; Hamel, M.; Casa, D.; Hosokawa, Y.; Morais, J.A.; Goulet, E.D.B. Wireless Measurement of Rectal Temperature during Exercise: Comparing an Ingestible Thermometric Telemetric Pill Used as a Suppository against a Conventional Rectal Probe. J. Therm. Biol. 2019, 83, 112–118.