Bio-electrical impedance analysis

Rationale: Diagnosis of sarcopenia in older adults is essential for early treatment in clinical practice. Bio-electrical impedance<br/>analysis (BIA) may be a valid means to assess appendicular lean mass (ALM) in older adults, but limited evidence is available.<br/>Therefore, we aim to evaluate the validity of BIA to assess ALM in older adults.<br/>Methods: In 215 community dwelling older adults (age ≥ 55 years), ALM was measured by BIA (Tanita MC-780; 8-points) and<br/>compared with dual-energy X-ray absorptiometry (DXA, Hologic Discovery A) as reference. Validity for assessing absolute values of<br/>ALM was evaluated by: 1) bias (mean difference), 2) percentage of accurate predictions (within 5% of DXA values), 3) individual<br/>error (root mean squared error (RMSE), mean absolute deviation), 4) limits of agreement (Bland-Altman analysis). For diagnosis of<br/>low ALM, the lowest quintile of ALM by DXA was used (below 21.4 kg for males and 15.4 for females). Sensitivity and specificity<br/>of detecting low ALM by BIA were assessed.<br/>Results: Mean age of the subjects was 71.9 ± 6.4, with a BMI of 25.8 ± 4.2 kg/m2, and 70% were females. BIA slightly<br/>underestimated ALM compared to DXA with a mean bias of -0.6 ± 0.2 kg. The percentage accurate predictions was 54% with<br/>RMSE 1.6 kg and limits of agreements -3.0 – +1.8 kg. Sensitivity was 79%, indicating that 79% of subjects with low ALM<br/>according to DXA also had low ALM with the BIA. Specificity was 90%, indicating that 90% of subjects with ‘no low’ ALM<br/>according to DXA also had ‘no low’ ALM with the BIA.<br/>Conclusions: This comparison showed a poor validity of BIA to assess absolute values of ALM, but a reasonable sensitivity and<br/>specificity to diagnose a low level of ALM in community-dwelling older adults in clinical practice.