title: The evaluation of consistency between body composition assessments in pediatric population using pencil beam and fan beam dual-energy x-ray absorptiometers.
abstract: The replacement of the old dual-energy X-ray absorptiometry system with a novel one should be preceded by a cross-calibration procedure. Therefore, the study was aimed at investigating the consistency of bone and body composition measures performed in pediatric population using pencil beam (DPX-L; GE Healthcare, GE Healthcare, Madison, WI) and fan beam (Prodigy; GE Healthcare, GE Healthcare, Madison, WI) densitometers. The study group consisted of 212 healthy children aged 4-18yr. Total body (TB) and lumbar spine (S) (L2-L4) measurements were performed using DPX-L and Prodigy during the same visit. Bland-Altman analysis, linear regressions, and paired t-test were performed to evaluate the consistency of measurements and to establish a cross-calibration equation. The average Prodigy values for TB and lumbar spine bone mineral density (BMD) and content (BMC) were 2.7%, 2.4% and 1.6%, 1.6% higher than those of DPX-L, respectively (p<0.0001). Prodigy-assessed bone area (BA) was lower by 1.4% for TBBA (p<0.0001) and 1.1% for SBA (p<0.001). Lean body mass (LBM) from Prodigy was higher by 6.9% (p<0.0001), whereas fat mass (FM) was lower by 8.4% compared with those from DPX-L (p<0.0001). Bland-Altman analyses revealed the effect of magnitude that was nonlinear (2nd degree polynomial) for TBBMD (r=0.32, p=0.001), TBBMC (r=0.51, p<0.0001), TBBA (r=0.34, p<0.0001), and LBM (r=0.56, p<0.0001), but not for FM (r=0.14, not significant [n.s.]). In contrast, in lumbar spine, the magnitude dependence was linear and significant for SBMC (r=0.46, p<0.0001) and SBA (r=0.34, p<0.0001) but not for SBMD (r=0.12, n.s.). Both skeletal and body composition variables assessed by DPX-L and Prodigy devices were highly correlated, showing R(2) values ranging from 0.976 for FM to 0.994 for SBMC. The results of this study document a necessity for implementation of calculated cross-calibration equations to transform DPX-L-based local pediatric references into a novel Prodigy system.
authors.affiliation: The Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland. Electronic address: p.pludowski@czd.pl.
authors.forename: Pawel
authors.initials: P
authors.lastname: Pludowski
authors.affiliation: The Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Jaworski
authors.affiliation: The Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Halina
authors.initials: H
authors.lastname: Matusik
authors.affiliation: The Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Kobylinska
authors.affiliation: The Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Paulina
authors.initials: P
authors.lastname: Klimek
authors.affiliation: The Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Roman S
authors.initials: RS
authors.lastname: Lorenc
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation*; D000293:Adolescent; D001824:Body Constitution / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D001846:Bone Development / Q000502:physiology*; D002138:Calibration; D002648:Child; D002675:Child, Preschool; D004867:Equipment Design; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D015203:Reproducibility of Results