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. (C) 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.