Body composition measurement in young children using quantitative magnetic resonance: a comparison with air displacement plethysmography

Background: Quantitative magnetic resonance (QMR) has been increasingly used to measure human body composition, but its use and validation in children is limited. Objective: We compared body composition measurement by QMR and air displacement plethysmography (ADP) in preschool children from Singapore's multi-ethnic Asian population (n = 152; mean +/- SD age: 5.0 +/- 0.1 years). Methods: Agreements between QMR-based and ADP-based fat mass and fat mass index (FMI) were assessed using intraclass correlation coefficient (ICC), reduced major axis regression and Bland-Altman plot analyses. Analyses were stratified for the child's sex. Results: Substantial agreement was observed between QMR-based and ADP-based fat mass (ICC: 0.85) and FMI (ICC: 0.82). Reduced major axis regression analysis suggested that QMR measurements were generally lower than ADP measurements. Bland-Altman analysis similarly revealed that QMR-based fat mass were (mean difference [95% limits of agreement]) -0.5 (-2.1 to +1.1) kg lower than ADPbased fat mass and QMR-based FMI were -0.4 (-1.8 to +0.9) kg/m(2) lower than ADP-based FMI. Stratification by offspring sex revealed better agreement of QMR and ADP measurements in girls than in boys. Conclusions: QMR-based fat mass and FMI showed substantial agreement with, but was generally lower than, ADP-based measures in young Asian children.