Inter- and Intra-Day Precision of a Low-Cost and Wearable Bioelectrical Impedance Analysis Device

Bioimpedance analysis (BIA) is a non-invasive and safe method to measure body composition. Nowadays, due to technological progress, smaller and cheaper devices allow the implementation of BIA into wearable devices. In this pilot study, we analyzed the measurement precision of a cheap BIA solution for wearable devices. Intra-session, intra-day, and inter-day reproducibility of raw impedance values from three subjects at three different body locations (hand-to-hand, hand-to-torso, torso-to-torso), and for three different frequencies (6, 54, and 500 kHz) were analyzed using the coefficient of variation (CV%). Hand-to-hand and hand-to-torso measurements resulted, on average, in high intra-session (CV% = 0.14% and CV% = 0.11%, respectively), intra-day (CV% = 1.67% and CV% = 1.26%, respectively), and inter-day (CV% = 1.53% and CV% = 1.31%) precision. Absolute impedance values for the torso-to-torso measurements showed a larger mean variation (intra-session CV% = 0.68%; intra-day CV% = 5.53%, inter-day CV% = 3.13%). Overall, this cheap BIA solution shows high precision and promising usability for further integration into a wearable measurement environment.