Toward Clinically Feasible Assessment of Muscle Mass: Validation of a Seated Bioelectrical Impedance Device Against Dual-Energy X-Ray Absorptiometry (DXA) in Older Adults.

Background

Although dual-energy X-ray absorptiometry (DXA) is the reference method for measuring appendicular skeletal muscle mass (ASMM) and diagnosing sarcopenia, seated bioelectrical impedance analysis (BIA) may represent a practical alternative. As its validity remains still insufficiently documented in specific populations, the objective is to evaluate the agreement between seated BIA and DXA, and examine associations between phase angle (PhA) and physical performance in old adults.

Methods

Fifty-nine old adults (75 ± 7 years) underwent DXA and seated BIA (Biody XpertZM3). ASMM was estimated using the Kyle and Sergi equations. Agreement with DXA was assessed using Lin's concordance correlation coefficient (CCC), Bland-Altman analysis, root mean square error (RMSE) and mean absolute error (MAE). Associations between PhA, handgrip strength, and five-times sit-to-stand (5-STS) performance were evaluated.

Results

Both equations showed good agreement with DXA, but the Sergi equation performed better, with higher concordance (CCC = 0.942 vs. 0.898), lower bias (0.44 vs. 1.11 kg), and lower RMSE (1.33 vs. 1.96 kg). PhA correlated positively with handgrip strength (r = 0.315, p = 0.015) but was not associated with 5-STS.

Conclusions

Seated BIA provides clinically acceptable estimates of ASMM in older adults. The Sergi equation demonstrated superior accuracy, supporting population-specific equations. PhA may provide additional information on muscle quality and sarcopenia.