234 ESTIMATION OF SKELETAL MUSCLE MASS BY DUAL-ENERGY X-RAY ABSORPTIONMETRY APPENDICULAR LEAN SOFT MASS IN CHINESE ADULT

Objective: We studied whether total body skeletal muscle (SM) mass could be accurately estimated from appendicular lean soft tissue (ALST) mass measured by dual-energy X-ray absorptionmetry (DXA), and investigated the validity of equations of prediction reported previously and derived from the data of the present study. Methods: We measured body composition by magnetic resonance imaging (MRI) and DXA in 194 Chinese stratified for sex, age and body mass index. The equation of prediction was generated by linear regression. The agreement between measured and predicted SM mass was assessed by the use of intraclass correlation analysis, paired t test, Bland-Altman plot.Results: The total body SM mass measured by MRI (18.1±4.8 kg) was closely correlated with ALST mass (19.4±4.7 kg), with a correlation coefficient of 0.95, 0.84 and 0.89 in all subjects, men and women, respectively. If the previously published equations were used, the difference of SM mass measured by MRI and estimated from ALST was 3.37±1.75 kg and 3.25±1.70 kg in the absence and presence of age in the equation, respectively. On the basis of our own data, we generated 2 equations without or with age: SM=0.98*ALST-0.99 (R2=0.91, P<0.0001) and SM=0.97 * ALST-0.03*Age+0.66 (R2=0.92, P<0.0001). By the application of these equations, the difference between measured and estimated SM mass decreased to -0.05±1.46 kg and -0.03±1.39 kg, respectively.Conclusions: Estimation of SM mass by ALST is plausible, but requires population-specific equations of prediction. Our equations should be validated in other studies in Chinese.