Which is the best alternative to estimate muscle mass for sarcopenia diagnosis when DXA is unavailable?

Dual x-ray absorptiometry (DXA) is widely adopted to estimate muscle mass for research, but for daily practice is only available in a limited number of facilities.

To elucidate if it is anthropometry or bioelectrical impedance analysis (BIA) the method more concordant with DXA in estimating muscle mass for sarcopenia diagnosis among older adults, and to investigate the impact of several cut-off points in sarcopenia frequency.

159 older adults (≥65 years) were included in a cross-sectional analysis. Sarcopenia was identified using the 2018 EWGSOP2 definition, plus previous definitions for muscle mass. Estimation of muscle mass by DXA (appendicular skeletal muscle mass (ASM) and ASM/height²), by BIA (skeletal muscle mass/height² (SMM/height²) and skeletal muscle mass index (SMI)), and anthropometry (calf and mid-arm muscle circumferences (CC and MAMC, respectively)) was carried out, as well as measurements of handgrip strength and gait speed.

Sarcopenia frequency varied from 5.0 to 42.1% depending on the method and cut-off point applied. All surrogate diagnostic criteria had a higher agreement with the DXA defined criterion ASM over ASM/height². A substantial agreement was also found with BIA SMM/height² (κ= 0.67), and with BIA SMI (κ= 0.65), and a moderate agreement with MAMC (κ= 0.42), p<0.001. Using the DXA ASM and ASM/height² criteria as reference, CC showed a specificity of 100% and 94%, respectively.

BIA is a suitable method to evaluate muscle mass in sarcopenia diagnosis when DXA is unavailable. Furthermore, CC showed to be a valid indicator to rule in the presence of sarcopenia.