Lack of agreement of in vivo raw bioimpedance measurements obtained from two single and multi-frequency bioelectrical impedance devices

Silva AM;Matias CN;Nunes CL;Santos DA;Marini E;Lukaski HC;Sardinha LB

2019-01-01

---

Abstract

Background: It is important for highly active individuals to accurately assess their hydration level. Bioelectrical impedance (BIA) can potentially meet these needs but its validity in active individuals is not well established. Methods: We compared whole-body bioimpedance measurements obtained from multi-frequency bioelectrical impedance spectroscopy (BIS, Xitron 4200) at a 50 kHz frequency with those determined by a phase-sensitive single-frequency device (SF-BIA, BIA-101, RJL/Akern Systems) in two populations: active adults and elite athletes. Results: One hundred twenty-six participants, including active males involved in recreational sports (N = 25, 20–39 yr) and elite athletes (females: N = 26, 18–35 yr; males: N = 75, 18–38 yr) participated in this study. Reactance (Xc), Resistance (R), Impedance (Z), and phase angle (PhA) were obtained by BIS and SF-BIA. Small but significant differences (R: −9.91 ± 15.09 Ω; Xc: −0.97 ± 2.56 Ω; Z: −9.96 ± 15.18 Ω; PhA: 0.12 ± 0.2°) were observed between the bioimpedance equipment in all measured variables (p < 0.05) though differences were within the devices’ technical error of measurements. Device-specific values were highly (p < 0.0001) correlated [R2 ranged from 0.881 (Xc) to 0.833 (R)], but slopes and intercepts were different (p < 0.0001) from 1 and 0, respectively. Relatively large limits of agreement were observed for R (−40 to 21 Ω), Xc (−6 to 4 Ω), PhA (−0.4 to 0.5°), and impedance (−40 to 20 Ω). Conclusion:: Bioimpedance measurements from the current single- and multi-frequency devices should not be used interchangeably. The of lack of agreement between devices was observed in determining individual values of R, Xc, Z and PhA of highly active populations possibly due to methodological and biological factors. © 2018, Springer Nature Limited.