Agreement between bioelectrical impedance analysis and dual-energy X-ray absorptiometry in Parkinson’s disease and controls

Abstract Background : Altered body composition is common in Parkinson’s disease (PD) and is associated with adverse clinical outcomes. Although dual-energy X-ray absorptiometry (DXA) is the reference method for body composition assessment, its limited availability restricts routine clinical use. This study compared body composition parameters obtained by bioelectrical impedance analysis (BIA) and DXA in individuals with PD and controls, evaluating agreement, consistency, and clinical applicability of BIA. Methods : In this cross-sectional study, 190 participants (95 with PD and 95 controls) underwent body composition assessment by BIA and DXA, including fat mass (FM), FM percentage, lean mass, appendicular lean mass (ALM), and appendicular lean mass index (ALMI). Agreement was assessed using Bland–Altman analysis, consistency with the intraclass correlation coefficient (ICC), and correlations with Spearman’s coefficient. Results : BIA showed strong correlations with DXA for all parameters (all p < 0.001), with excellent consistency. No significant differences were found for fat mass or fat mass percentage. However, in both groups, BIA significantly underestimated lean mass, ALM, and ALMI. Bland–Altman analyses demonstrated small mean bias but wide limits of agreement and proportional bias. Conclusions : BIA demonstrated strong correlation and excellent consistency with DXA in PD. However, systematic underestimation of lean mass–related parameters and wide limits of agreement limit its interchangeability with DXA at the individual level. BIA may still be useful for clinical screening and population-level assessment when DXA is unavailable.