The impact of equations on calculation of lean body mass by bioelectrical impedance analysis in RDT patients

Several equations are available to derive lean body mass (LBM) from bioelec trical impedance analysis (BIA). The purpose of this study was to investiga te in dialysis patients the impact of the equation used on the outcome of L BM assessment To avoid dyshydration as a confounder, vena cava diameter mea surement was used to assess normohydration in the 21 patients studied. Five equations were compared. In a previously published study to assess fetal body water using antipyrine as a gold standard, Deurenberg's formula was advocated to be used in the e stimation of LBM by BIA. Therefore, this formula was used as a basis for co mparison with the other four equations. One equation gave results comparabl e to those obtained by Deurenberg's formula. Despite high correlations and agreement according to Bland and Altman analysis, the other three equations showed a significant difference with Deurenberg-derived LBM. Thus, the equ ation used has a major impact on the outcome of LBM estimations.