Prediction and validation of DXA-derived appendicular lean soft tissue mass by ultrasound in older adults.

The purpose of this study was to develop regression-based prediction equations for estimating dual-energy X-ray absorptiometry (DXA)-derived appendicular lean soft tissue mass (aLM) using ultrasound and to investigate the validity of these equations in 102 Caucasian adults aged 50 to 76 years. The subjects were randomly separated into two groups: 71 in the model-development group (41 men and 30 women) and 31 in the cross-validation group (18 men and 13 women). aLM was measured using a DXA, and muscle thickness (MT) was measured using ultrasound at 9 sites. Stepwise linear regression analysis was used to determine predictive models for DXA-derived aLM from MT variables, sex, and age. A number of ultrasound prediction equations for estimation of aLM were developed and then cross-validated in a subsample of older adults. The results indicated that ultrasound MT and MT × height can be used to accurately and reliably estimate DXA-derived aLM in older Caucasian adults.