DXA-derived abdominal fat free mass to predict MRI skeletal muscle mass in postmenopausal women.

Dual-energy X-ray absorptiometry (DXA) is more available than gold-standard magnetic resonance imaging (MRI), but DXA ability to estimate abdominal skeletal muscle mass (SMM) is unknown. DXA-derived abdominal fat-free mass (FFM; Hologic QDR2000 or QDR4500w) was correlated with single-slice MRI SMM at L4 (N = 69; r QDR2000=0.71, QDR4500w=0.69; p<.0001). Linear regression to predict SMM, including DXA FFM, BMI, and age, resulted in an R-squared of 0.72 and 0.65 for QDR2000 and QDR4500. Bland-Altman limits of agreement were ±21g and ±31g for 2-3 standard deviations from the mean difference. DXA predicted abdominal SSM is a moderate proxy for MRI abdominal SMM.