Validity of bioelectrical impedance analysis to estimate body composition in patients with severe motor and...

Assessing nutritional status in patients with severe motor and intellectual disabilities (SMID) is essential but challenging. While dual-energy X-ray absorptiometry (DXA) is the standard method for body composition analysis, its clinical utility is limited by logistical constraints. This study aimed to evaluate the concurrent validity and agreement of bioelectrical impedance analysis (BIA) compared with DXA in patients with SMID.

Twelve patients with SMID (median age: 11 years) underwent body composition measurements using a multi-frequency BIA device and DXA. Agreement between the two methods for fat-free mass (FFM), body fat mass (BF), percentage body fat (%BF), and regional lean mass was assessed using intraclass correlation coefficients (ICCs) and Bland-Altman analysis.

BIA demonstrated excellent concurrent validity for whole-body absolute mass parameters, with ICCs of 0.981 for FFM and 0.978 for BF. Mean bias was minimal for FFM (0.3 kg) and BF (-0.3 kg). However, %BF showed lower validity (ICC = 0.813) and was substantially underestimated (mean bias -7.1%). Bland-Altman analysis revealed wide limits of agreement for all parameters and a significant proportional bias for BF, indicating overestimation as adiposity increased. Regional analysis showed high validity for the trunk but poor agreement for limb measurements.

IA is a useful non-invasive alternative for assessing FFM and BF at the group level in patients with SMID. However, caution is warranted for individual assessment, particularly for %BF, which BIA tends to underestimate in this population.