Assessing the Reliability and Cross-Sectional and Longitudinal Validity of 15 Bioelectrical Impedance Analysis Devices.

The purpose of this investigation was to expand upon the limited existing research examining the test-retest reliability, cross-sectional validity, and longitudinal validity of a sample of bioelectrical impedance analysis (BIA) devices as compared to a laboratory four-compartment (4C) model. Seventy-three healthy participants aged 19-50 were assessed by each of 15 BIA devices, with resulting body fat percentage (BFP) estimates compared to a 4C model utilizing air displacement plethysmography, dual-energy x-ray absorptiometry, and bioimpedance spectroscopy. A subset of 37 participants returned for a second visit 12-16 weeks later and were included in an analysis of longitudinal validity. The sample of devices included 14 consumer-grade and one-research grade model in a variety of configurations: hand-to-hand, foot-to-foot, and bilateral hand-to-foot (octapolar). BIA devices demonstrated high reliability, with precision error ranging from 0.0 to 0.49%. Cross-sectional validity varied, with constant error relative to the 4C model ranging from -3.5±4.1% to 11.7±4.7%, standard error of the estimate values of 3.1% to 7.5%, and Lin's concordance correlation coefficients of 0.48 to 0.94. For longitudinal validity, constant error ranged from -0.4±2.1% to 1.3±2.7%, with standard error of the estimate values of 1.7% to 2.6% and Lin's concordance correlation coefficients of 0.37 to 0.78. While performance varied widely across the sample investigated, select models of BIA devices (particularly octapolar and select foot-to-foot devices) may hold potential utility for the tracking of body composition over time, particularly in contexts in which the purchase or use of a research-grade device is infeasible.