Location: Arkansas Children's Nutrition CenterTitle: QMR: Validation of an infant and children body composition instrument using piglets against chemical analysis) Author
Submitted to: International Journal of Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2009
Publication Date: 4/11/2010
Citation: Andres, A., Mitchell, A.D., Badger, T.M. 2010. QMR: Validation of an infant and children body composition instrument using piglets against chemical analysis. International Journal of Obesity. 34(4):775-80. Interpretive Summary: The current study was undertaken to validate the first quantitative nuclear magnetic resonance instrument designed and built to assess body composition from birth through adulthood (up to 110 lbs). Piglets were used to validate the instrument against three other body composition methods: dual-energy X-ray Absorptiometry, air displacement plethysmography, and chemical carcass analyses. The precision and accuracy of the new technology was excellent for fat mass, fat free mass, and total body water. Quantitative nuclear magnetic resonance is a very promising technology that will allow longitudinal acquisition of data sets in the pediatric population.
Technical Abstract: The current study was undertaken to validate the first quantitative nuclear magnetic resonance instrument designed and built to assess body composition from birth through adulthood (up to 50 kg). A total of 50 pigs weighing between 3.0 and 49.1 kg were studied. Each piglet's body composition was assessed via Dual Energy X-ray Absorptiometry (DXA, Hologic QDR 4500), Quantitative Nuclear Magnetic Resonance (QMR, EchoMRI-AH small), and whole body chemical carcass analysis. DXA and QMR were repeated 5 times with repositioning to assess precision. Twenty-five piglets (3.1 to 47.2 kg) were randomly selected to calibrate the QMR instrument. The remainder 25 piglets (3.0 to 49.1 kg) were used to validate the instrument. The precision (coefficients of variation) of the QMR to estimate fat mass (FM), fat free mass (FFM) and total body water (TBW) for 5 consecutive scans was excellent (1.3%, 0.9% and 0.9%, respectively). QMR measures of FM were highly and significantly correlated with chemical carcass analyses and DXA measures (r2=0.99 and r2=0.97, respectively). Compared with the carcass lipid analyses, DXA overestimated FM by 15% on average (approx. 400 g); whereas, QMR overestimated FM by 2% on average (43 g). DXA and QMR FFM results were highly correlated (R2=0.99, P<0.01). Total body water measures were highly correlated between the QMR and carcass analyses (R2=0.99, P<0.01). QMR provide precise and accurate measures of FM, FFM, and TBW in piglets weighing up to 50 kg. This new technology is very promising and will allow longitudinal acquisition of data sets in the pediatric population, which has been, up to now, a major challenge.