Background: The diagnosis of sarcopenia is essential for early treatment of sarcopenia in older adults, for which assessment of appendicular lean mass (ALM) is needed. Multi-frequency bio-electrical impedance analysis (MF-BIA) may be a valid assessment tool to assess ALM in older adults, but the evidences are limited. Therefore, we validated the BIA to diagnose low ALM in older adults.Methods: ALM was assessed by a standing-posture 8 electrode MF-BIA (Tanita MC-780) in 202 community-dwelling older adults (age ≥ 55 years), and compared with dual-energy X-ray absorptiometry (DXA) (Hologic Inc., Marlborough, MA, United States; DXA). The validity for assessing the absolute values of ALM was evaluated by: (1) bias (mean difference), (2) percentage of accurate predictions (within 5% of DXA values), (3) the mean absolute error (MAE), and (4) limits of agreement (Bland-Altman analysis). The lowest quintile of ALM by DXA was used as proxy for low ALM (< 22.8 kg for men, < 16.1 kg for women). Sensitivity and specificity of diagnosing low ALM by BIA were assessed.Results: The mean age of the subjects was 72.1 ± 6.4 years, with a BMI of 25.4 ± 3.6 kg/m2, and 71% were women. BIA slightly underestimated ALM compared to DXA with a mean bias of -0.6 ± 1.2 kg. The percentage of accurate predictions was 54% with a MAE of 1.1 kg, and limits of agreement were -3.0 to + 1.8 kg. The sensitivity for ALM was 80%, indicating that 80% of subjects who were diagnosed as low ALM according to DXA were also diagnosed low ALM by BIA. The specificity was 90%, indicating that 90% of subjects who were diagnosed as normal ALM by DXA were also diagnosed as normal ALM by the BIA.Conclusion: This comparison showed a poor validity of MF-BIA to assess the absolute values of ALM, but a reasonable sensitivity and specificity to recognize the community-dwelling older adults with the lowest muscle mass.
Rationale: Diagnosis of sarcopenia in older adults is essential for early treatment in clinical practice. Bio-electrical impedanceanalysis (BIA) may be a valid means to assess appendicular lean mass (ALM) in older adults, but limited evidence is available.Therefore, we aim to evaluate the validity of BIA to assess ALM in older adults.Methods: In 215 community dwelling older adults (age ≥ 55 years), ALM was measured by BIA (Tanita MC-780; 8-points) andcompared with dual-energy X-ray absorptiometry (DXA, Hologic Discovery A) as reference. Validity for assessing absolute values ofALM was evaluated by: 1) bias (mean difference), 2) percentage of accurate predictions (within 5% of DXA values), 3) individualerror (root mean squared error (RMSE), mean absolute deviation), 4) limits of agreement (Bland-Altman analysis). For diagnosis oflow ALM, the lowest quintile of ALM by DXA was used (below 21.4 kg for males and 15.4 for females). Sensitivity and specificityof detecting low ALM by BIA were assessed.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 slightlyunderestimated ALM compared to DXA with a mean bias of -0.6 ± 0.2 kg. The percentage accurate predictions was 54% withRMSE 1.6 kg and limits of agreements -3.0 – +1.8 kg. Sensitivity was 79%, indicating that 79% of subjects with low ALMaccording to DXA also had low ALM with the BIA. Specificity was 90%, indicating that 90% of subjects with ‘no low’ ALMaccording to DXA also had ‘no low’ ALM with the BIA.Conclusions: This comparison showed a poor validity of BIA to assess absolute values of ALM, but a reasonable sensitivity andspecificity to diagnose a low level of ALM in community-dwelling older adults in clinical practice.
Rationale: Sarcopenia is a major problem and is common in community-dwelling elderly. In daily practice, there is need for low cost and easily assessable measurement tools to assess depletion of skeletal muscle (SM) mass, for example as one of the indicators of sarcopenia. Bio-electrical impedance analysis (BIA) is often used to estimate body composition, whereas ultrasound measurement is an upcoming and promising tool, as it is quick, easy to use and inexpensive in comparison with other tools that assess SM mass. Ultrasound could assess site-specific loss of SM mass and determine myoesteatosis. Therefore, in this pilot study we aimed to assess agreement between muscle thickness of rectus femoris (RF) by ultrasound and SM mass by BIA in an older population. Methods: Twenty-six older adults (mean± standard deviation (SD) age 64 ±5.0 y, 62% women) from the Hanze Health and Ageing Study were included. SM mass by BIA was estimated using the Janssen equation. Muscle thickness of RF was assessed by analyzing ultrasound images from the right leg. Two non-parametric tests were used for analysis. Correlation between ultrasound and BIA was assessed with Spearman Rho. Agreement was determined with Kendall’s coefficient of concordance (Kendall’s W). In both tests a score ≥ 0.7 was considered a strong correlation.Results: Mean (±SD) RF thickness was 18.9 (±3.8) mm. Median SM mass (Interquartile range) was 23.5 (20.8-34.7) kg. Correlation between RF thickness and SM mass was moderately positive (Spearman r=0.611; P = 0.001), whereas Kendall’s W showed a strong agreement (W= 0.835; P=0.002).Conclusion: Ultrasound measurement of RF showed an acceptable agreement with skeletal muscle mass assessed by BIA in our sample of older adults. Therefore, ultrasound could be a promising portable tool to estimate muscle size.
