Use of different segmental multi-frequency bioelectrical impedance devices for analysis of body composition in young adults: comparison with bioelectrical spectroscopy.

Introduction: recently there have been several new versions of equipment based on the principles of bioelectrical impedance (BIA). Therefore, it is important to know the agreement between data produced by different commercially available equipment. Objective: to verify the agreement between fat-free mass (FFM), fat mass (FM), and body fat percentage (BF%) estimated using different segmental multi-frequency BIA (Tanita® MC-980U and InBody 770®) and whole-body spectral techniques (Xitron 4200). Methods: the sample consisted of 117 adults of both sexes, aged between 18 and 28 years. Methodological procedures followed specific guidelines for each equipment model. Agreement was analyzed by the t-test for paired data, concordance correlation coefficient (CCC), and Bland-Altman plot. Results: mean estimates of FFM, FM, and BF% produced by the Tanita® MC-980U and InBody 770® devices did not present statistical differences compared to the Xitron 4200® reference device. CCC values for FFM demonstrated magnitudes between 0.904 and 0.931, representing clinically acceptable strength of agreement, while for FM and BF% the strength of agreements was weak (< 0.90). Regarding the FFM, the bias showed underestimates of -0.98 kg to -1.69 kg, with limits of agreement between -7.32 kg and 3.94 kg. In the case of FM and BF%, overestimations were observed that reached values of 1.01 kg and 0.71%, with limits of agreement of -1.91 kg to 3.93 kg and -3.86% to 5.28%, respectively. Conclusion: FFM, FM, and BF% estimated by the Tanita® MC-980U and InBody 770® devices were not individually comparable with estimates produced by the Xitron 4200® reference device; therefore, its replacement for diagnostic purposes and inter- or intra-subject comparisons is not recommended.