Validity and reliability of the myTemp ingestible temperature capsule

Objectives

An accurate and non-invasive measurement of core body temperature (Tc) is of great importance to quantify exercise-induced increases in Tc in athletes or to assess changes in Tc in patient populations. The use of ingestible gastrointestinal telemetric temperature capsules is widely accepted as a surrogate marker for Tc, but widespread implementation is lacking due to the high costs of these disposable capsules. A new and cheaper temperature capsule system (i.e. myTemp) was recently introduced. The aim of present study is to determine the validity and test–retest reliability of the myTemp system.

Design

Ex-vivo experimental study.

Methods

Fifteen ingestible temperature capsules (myTemp, Nijmegen, Netherlands) were tested in a highly temperature controlled water bath, in which the water temperature gradually increased from 34 °C to 44 °C. The study protocol was performed twice for each temperature capsule.

Results

Mean difference between myTemp temperature and water bath temperature was ?0.001 ± 0.005 °C (Limit of Agreement (LOA): ±0.011 °C) during Trial 1 (p = 0.11) and ?0.001 ± 0.006 °C (LOA: ±0.012 °C) during Trial 2 (p = 0.039). Furthermore, an Intraclass Correlation Coefficient (ICC) of 1.00 was found for both trials. A systematic difference between Trials 1 and 2 of 0.004 ± 0.008 °C (LOA: ±0.015 °C) was found (p < 0.001), whereas the ICC between both trials was 1.00 and the standard error of measurement was 0.005 °C.

Conclusions

Although we found a systematic bias for the sensitivity (?0.001 °C) and reliability (0.004 °C), these values can be considered insignificant from a physiological and clinical perspective. Thus, the myTemp ingestible temperature capsule is a valid technique to measure (water) temperature under controlled circumstances.