Validity, Reliability, and Inertia of Four Different Temperature Capsule Systems

Purpose Telemetric temperature capsule systems are wireless, relatively noninvasive, and easily applicable in field conditions and have therefore great advantages for monitoring core body temperature. However, the accuracy and responsiveness of available capsule systems have not been compared previously. Therefore, the aim of this study was to examine the validity, reliability, and inertia characteristics of four ingestible temperature capsule systems (i.e., CorTemp, e-Celsius, myTemp, and VitalSense). Methods Ten temperature capsules were examined for each system in a temperature-controlled water bath during three trials. The water bath temperature gradually increased from 33 degrees C to 44 degrees C in trials 1 and 2 to assess the validity and reliability, and from 36 degrees C to 42 degrees C in trial 3 to assess the inertia characteristics of the temperature capsules. Results A systematic difference between capsule and water bath temperature was found for CorTemp (0.077 degrees C 0.040 degrees C), e-Celsius (-0.081 degrees C +/- 0.055 degrees C), myTemp (-0.003 degrees C +/- 0.006 degrees C), and VitalSense (-0.017 degrees C +/- 0.023 degrees C; P < 0.010), with the lowest bias for the myTemp system (P < 0.001). A systematic difference was found between trial 1 and trial 2 for CorTemp (0.017 degrees C +/- 0.083 degrees C; P = 0.030) and e-Celsius (-0.007 degrees C +/- 0.033 degrees C; P = 0.019), whereas temperature values of myTemp (0.001 degrees C +/- 0.008 degrees C) and VitalSense (0.002 degrees C +/- 0.014 degrees C) did not differ (P > 0.05). Comparable inertia characteristics were found for CorTemp (25 +/- 4 s), e-Celsius (21 +/- 13 s), and myTemp (19 +/- 2 s), whereas the VitalSense system responded more slowly (39 +/- 6 s) to changes in water bath temperature (P < 0.001). Conclusions Although differences in temperature and inertia were observed between capsule systems, an excellent validity, test-retest reliability, and inertia was found for each system between 36 degrees C and 44 degrees C after removal of outliers.