Measurement error in bioimpedance spectroscopy: The role of electrode type and analyzer

Bioimpedance spectroscopy (BIS) is a non-invasive method used to assess body composition in a variety of settings. Although BIS has been reported as an accurate measure of body composition, the magnitude of within-day technical error associated with different BIS devices and electrode types remains unknown. Therefore, the purpose of this study was to assess the technical error of measurement (TEM) between single-tab and double-tab electrodes across two BIS devices for resistance, reactance, phase angle, total body water, fat-free mass, and fat mass. One hundred and four adults reported to the laboratory for a single visit, undergoing twelve different assessments utilizing single- and double-tab electrodes on two BIS analyzers of the same model. The within-day technical error was assessed as the absolute and relative TEM for each of the variables. The results indicated that intra-analyzer assessments displayed the lowest amount of error for all the variables (relative TEM = 0.05 - 0.28%) while the largest TEMs were observed for comparisons between single-tab and double-tab assessments (relative TEM = 1.04 - 3.68%), except for reactance. For reactance alone, the TEMs were greatest for the inter-analyzer comparison with double-tab electrodes (absolute TEM = 1.07 Ω; relative TEM = 1.68%). While all assessments displayed relatively low technical error, the present results reinforce the importance of consistently using the same analyzer and electrode type to minimize errors when assessing body composition using BIS, particularly when seeking to identify subtle changes in BIS output.