title: Importance of lean mass in the interpretation of total body densitometry in children and adolescents.
abstract: OBJECTIVE
  Most studies that use total body dual energy x-ray absorptiometry (DEXA) in children rely on areal bone mineral density (BMD=bone mineral content [BMC]/bone area [BA]) and compare the output with age- and sex-specific normative data. Because this approach is prone to size-related misinterpretation, this study focuses on the interrelations among BMC, body size (height), and lean tissue mass (LTM).
  
  
  METHODS
  This cross-sectional study presents normative total body LTM data in relation to height and BMC for 459 healthy white subjects (249 female), 3 to 30 years of age. Guidelines for DEXA interpretation in children are provided and illustrated for patients with growth hormone deficiency (n=5) and anorexia nervosa (n=5).
  
  
  RESULTS
  LTM/height tended to be greater in male than in girls. The BMC/LTM ratio was greater in female than in boys (P<.001), even after adjustment for age and height. Sex-specific reference curves were created for LTM/height, the BMC/LTM ratio, BA/height, and BMC/BA.
  
  
  CONCLUSIONS
  We recommend that total body DEXA in children should be interpreted in 4 steps: (1) BMD or BMC/age, (2) height/age, (3) LTM/height, and (4) BMC/LTM ratio for height. This allows differentiation of the origin of a low BMD or BMC/age, for example, short stature and primary, secondary, and mixed bone defects.
authors.affiliation: Institute of Endocrinology and Diabetes, the Department of Nuclear Medicine, The Children's Hospital at Westmead, Sydney, NSW, Australia.
authors.forename: W
authors.initials: W
authors.lastname: Högler
authors.forename: J
authors.initials: J
authors.lastname: Briody
authors.forename: H J
authors.initials: HJ
authors.lastname: Woodhead
authors.forename: A
authors.initials: A
authors.lastname: Chan
authors.forename: C T
authors.initials: CT
authors.lastname: Cowell
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation*; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001827:Body Height; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006130:Growth Disorders / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D008297:Male; D017678:Sex Distribution