title: Comparison of Hologic QDR-1000/W and 4500W DXA Scanners in 13- to 18-Year Olds.
abstract: OBJECTIVE
  Body composition measurements made using Hologic QDR-1000/W pencil-beam and QDR-4500W fan-beam scanners (Bedford, MA) were compared in a sample of 13- to 18-year-old white and black youth (n = 219).
  
  
  METHODS
  Total fat (FAT), fat-free soft tissue (FFST), bone mineral content (BMC), bone mineral density (BMD), and percent body fat (%BF) were compared between repeated measurements using the QDR-4500 and between the two scanners using mixed model ANOVA. Intraclass correlation coefficients and Bland-Altman limits of agreement were used to evaluate inter- and intrascanner reliability.
  
  
  RESULTS
  Intraclass correlation coefficients for repeated measurements using the QDR-4500 ranged from 0.997 to 0.999 for FAT, %BF, FFST, and BMC and 0.987 for BMD. Mean measurements made using the two scanners differed significantly for FAT, %BF, BMC, and BMD (p < 0.0001), and scan by sex interactions were significant (all p < 0.0005). There were no significant differences in mean measurements between repeat scans using the QDR-4500 (all p > 0.19). Limits of agreement for measurements of FAT, FFST, and %BF made using the two scanners were approximately three times as wide as those for two measurements using the QDR-4500. For lower values of FAT and %BF, the QDR-4500 gave higher measurements than the QDR-1000, whereas at higher values, this relationship was reversed. The QDR-1000 tended to give higher BMC measurements, with larger differences for higher values.
  
  
  CONCLUSIONS
  Using different models of DXA scanners within a study may reduce precision of body composition measurement. This issue needs to be considered in the design of longitudinal studies.
authors.affiliation: Office of Biostatistics and Bioinformatics, Georgia Prevention Institute, Augusta, Georgia 3912-4900, USA. mlitaker@mail.mcg.edu
authors.forename: Mark S
authors.initials: MS
authors.lastname: Litaker
authors.forename: Paule
authors.initials: P
authors.lastname: Barbeau
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Humphries
authors.forename: Bernard
authors.initials: B
authors.lastname: Gutin
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation*; D000273:Adipose Tissue / Q000502:physiology; D000293:Adolescent; D001741:Black or African American; D000886:Anthropometry / Q000295:instrumentation* / Q000379:methods; D001823:Body Composition / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D044465:White People