Evaluation of DXA vs. MRI for body composition measures in 1-month olds

Background: Detailed measures of infant body composition are needed for understanding the impact of genes and environment on growth early in life. Objective: The purpose of this study was to compare the accuracy and bias of body composition in infants. Methods: Dual energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) were used to determine body composition and the trunk depot. The depots measured were total fat mass (FM), total fat-free mass (FFM) and trunk FM and FFM using DXA and MRI in 14 infants. Results: None of the regression lines between DXA and MRI significantly deviate from the line of identity for any of the depots studied. However, Bland-Altman analyses revealed bias for trunk FM and trunk FFM. Conclusion: Our data showed DXA to be accurate (regression not significantly deviating from the line of identity), with high agreement (indicated by high R-2) and without bias (non-significant Bland-Altman) when estimating total FM and FFM. This could not be said for trunk estimates.