Comparison Of Total Body And Thigh Mineral-free Lean Measures Using DXA In Young Children

BACKGROUND: Total body composition assessment using MRI or CT scan can provide both quantitative and qualitative assessment of tissue masses; however, they are cost, time and safety prohibitive. Alternatively, cross-sectional slices of the thigh using these MRI- or CT-based techniques have previously been used to represent baseline and changes in skeletal muscle mass due to training, treatment, and rehabilitation strategies. More recently, the total body mineral-free lean mass (MFLM) measures via DXA scanning have been used to quantitatively represent total skeletal muscle mass despite known assumption violations and an inability to distinguish among skeletal muscle mass, viscera and fluids. Since uniquely created regions of interest (ROIs) are possible with DXA scanning, the purpose of this study was to determine if there is a significant association between total body and thigh MFLM (which contains no viscera) using DXA scanning in young children. METHODS: We enrolled and tested 75 (36 boys) children 5-11 years (Mean ± SD: 8.9 ± 1.8 yrs) of age. Total body DXA scans were acquired for each participant. Subsequently, a single trained investigator used the DXA custom analyses software to analyze the right thigh MFLM twice and the mean of the measurements was used for final analyses. RESULTS: Total thigh MFLM (2.95 ± 1.1 kg) explained 97.4% of the variance in total body MFLM (23.4 ± 7.1 kg). CONCLUSIONS: The unique ROIs analyses demonstrated a strong association between total thigh and total body MFLM confirmed by the significant explained variance. Based on these results, total thigh MFLM may be considered a useful predictor of total body MFLM, and conversely total body MFLM may more confidently be used to represent total body skeletal muscle mass in young children.