BIA demonstrated excellent concurrent validity for whole-body absolute mass parameters (FFM and BF) but showed lower validity and substantial underestimation of %BF, with wide limits of agreement for all parameters, suggesting BIA is useful at the group level but requires caution for individual assessment in patients with SMID.
BIA showed excellent concurrent validity for whole-body fat-free mass compared to DXA in patients with severe motor and intellectual disabilities.
BIA showed excellent concurrent validity for whole-body body fat mass but demonstrated a significant proportional bias as adiposity increased.
BIA substantially underestimated percentage body fat (%BF) and showed lower validity for this parameter compared to DXA.
Regional body composition analysis showed high validity for trunk measurements but poor agreement for limb measurements.
BIA is considered a useful non-invasive alternative to DXA for group-level assessment of FFM and BF in patients with SMID, but not for individual-level assessment.
This research suggests that a common body composition measurement tool called bioelectrical impedance analysis (BIA) — which works by sending a small electrical current through the body — can be a practical substitute for the gold-standard method (DXA, or dual-energy X-ray absorptiometry) when measuring overall body fat and lean mass in children and patients with severe motor and intellectual disabilities (SMID). The study found that BIA agreed very closely with DXA when measuring total fat mass and fat-free mass across 12 patients with SMID, with the two methods differing by less than half a kilogram on average. This is meaningful because DXA machines are large, expensive, and difficult to use with patients who have movement limitations, whereas BIA is portable and non-invasive. However, the study also found important limitations. BIA consistently underestimated the percentage of the body made up of fat (by about 7 percentage points on average), and for patients with higher body fat levels, BIA tended to overestimate fat mass. Additionally, while BIA performed well for measuring trunk (torso) lean mass, it performed poorly for measuring lean mass in the arms and legs. The range of measurement differences between BIA and DXA was also wide for all parameters, meaning the tools could disagree substantially in any individual patient. This research suggests that BIA may be a useful screening or monitoring tool when looking at trends across groups of SMID patients, but it should be used with caution when making decisions about a specific individual's body composition, especially regarding body fat percentage. Clinicians working with SMID populations should be aware of these limitations when interpreting BIA results.
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Upload Your LabsKurima T, Shimizu Y, Hada Y, Nakayama T. (2026). Validity of bioelectrical impedance analysis to estimate body composition in patients with severe motor and intellectual disabilities.. Brain & development. https://doi.org/10.1016/j.braindev.2026.104536