Reliability of multiple frequency bioelectrical impedance analysis: An intermachine comparison

Abstract

The technical reliability (i.e., interinstrument and interoperator reliability) of three SEAC‐swept frequency bioimpedance monitors was assessed for both errors of measurement and associated analyses. In addition, intraoperator and intrainstrument variability was evaluated for repeat measures over a 4‐hour period. The measured impedance values from a range of resistance‐capacitance circuits were accurate to within 3% of theoretical values over a range of 50–800 ohms. Similarly, phase was measured over the range 1°–19° with a maximum deviation of 1.3° from the theoretical value. The extrapolated impedance at zero frequency was equally well determined (±3%). However, the accuracy of the extrapolated value at infinite frequency was decreased, particularly at impedances below 50 ohms (approaching the lower limit of the measurement range of the instrument). The interinstrument/operator variation for whole body measurements were recorded on human volunteers with biases of less than ±1% for measured impedance values and less than 3% for phase. The variation in the extrapolated values of impedance at zero and infinite frequencies included variations due to operator choice of the analysis parameters but was still less than ±0.5%. Am. J. Hum. Biol. 9:63–72 © 1997 Wiley‐Liss, Inc.

Reference Ranges for Assessment of Unilateral Lymphedema in Legs by Bioelectrical Impedance Spectroscopy

“…when used to calculate R i . 11 The mean value for the inter-leg ratio of R 0 (dominant:nondominant) in females was very close to unity, 0.999 (AE0.056), while in males the value was slightly further from unity, 0.994 (AE0.050), reflecting the slight asymmetry seen in R 0 values. The impedance ratios were not significantly correlated with either BMI (r ¼ 0.054 and r ¼ 0.109 for females and males, respectively) or the age (r ¼ 0.117 and r ¼ 0.013 for females and males, respectively) of participants.…”

Confirmation of the Reference Impedance Ratios Used for Assessment of Breast Cancer-Related Lymphedema by Bioelectrical Impedance Spectroscopy

“…values between the SFB3 and SFB7 instruments have been determined when both are tested on participants or electronic test circuits. 9 Therefore, all SFB3 data were converted to equivalent SFB7 data using the conversion factors provided by Ward. 10 Data processing and analysis Data from both instruments were analyzed according to Cole theory, 11 using the manufacturer's software (Bioimp version 4.8.0.0, Impedimed Ltd.), to provide values for R 0 and R ?.…”

“…Generally, the default program settings were used for analyses; however, for some data sets, the analysis was optimized by adjustment of the frequency ''window'' used for fitting the data to the Cole model guided by minimizing the standard error of the estimate (SEE) for the curve fitting procedure. 9 The SEE for all analyses was <1%.…”

Experimental and Analytical Comparisons of Tissue Dielectric Constant (TDC) and Bioimpedance Spectroscopy (BIS) in Assessment of Early Arm Lymphedema in Breast Cancer Patients after Axillary Surgery and Radiotherapy

“…This indicates that such a 20% change in skin water would be essentially undetectable with multi-frequency BIS analyzers that have a reported accuracy of -3% for resistance R 0. 65 Using the same model it can be shown that for an increase of 20% in skin tissue water the arm volume changes less than 2% (i.e., such a 20% change in skin water volume is practically undetectable by arm volume measurement). Calculations based on this simple, but representative model, suggests that the main route of electric current in the BIS technique is through the well-conducting (subfascial) muscle component that is largely spared of swelling and to a lesser amount through the skin where early lymphedema is thought to manifest.…”