Dual-energy X-ray absorptiometry: analysis of pediatric fat estimate errors due to tissue hydration effects

• Published in: Journal of applied physiology (1985) 2000-12, Vol.89 (6), p.2365-2372
• Main Authors: Testolin, Corrado G, Gore, Robert, Rivkin, Tommy, Horlick, Mary, Arbo, John, Wang, Zimian, Chiumello, Giuseppe, Heymsfield, Steven B
• Format: Article
• Language: English
• Subjects: Absorptiometry, Photon; Adipose Tissue - diagnostic imaging; Adipose Tissue - metabolism; Biological and medical sciences; Body Composition; Body Water - metabolism; Child, Preschool; Fundamental and applied biological sciences. Psychology; General aspects; Humans; Models, Biological; Pediatrics - methods; Phantoms, Imaging; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2000.89.6.2365

1  Department of Pediatrics, San Raffaele Hospital, 20132 Milano, Italy; and 2  Obesity Research Center, St. Luke's/Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York, New York 10025 Dual-energy X-ray absorptiometry (DXA) percent (%) fat estimates may be inaccurate in young children, who typically have high tissue hydration levels. This study was designed to provide a comprehensive analysis of pediatric tissue hydration effects on DXA %fat estimates. Phase 1  was experimental and included three in vitro studies to establish the physical basis of DXA %fat-estimation models. Phase 2  extended phase 1  models and consisted of theoretical calculations to estimate the %fat errors emanating from previously reported pediatric hydration effects. Phase 1  experiments supported the two-compartment DXA soft tissue model and established that pixel ratio of low to high energy (R values) are a predictable function of tissue elemental content. In phase 2, modeling of reference body composition values from birth to age 120 mo revealed that %fat errors will arise if a "constant" adult lean soft tissue R value is applied to the pediatric population; the maximum %fat error, ~0.8%, would be present at birth. High tissue hydration, as observed in infants and young children, leads to errors in DXA %fat estimates. The magnitude of these errors based on theoretical calculations is small and may not be of clinical or research significance. body composition; total body fat; nutritional assessment