title: A comparison of body composition estimates using dual-energy X-ray absorptiometry and air-displacement plethysmography in South African neonates.
abstract: Neonatal body composition is an important predictor of future metabolic risk; however, the comparability of objective assessment techniques, particularly in African populations undergoing rapid health transition, is not known. This paper compares body composition estimates by air-displacement plethysmography (ADP) and dual-energy X-ray absorptiometry (DXA) in South African neonates.
  
  
  
  Fat mass, fat-free mass and body fat percentage (%fat) estimates by ADP and DXA were compared in 88 urban, black South African neonates. The level of agreement between the techniques was assessed using Bland-Altman analyses.
  
  
  
  Significant correlations were observed between ADP and DXA measurements of fat mass (r=0.766), fat-free mass (r=0.942) and %fat (r=0.630); however, ADP estimates of fat mass (408±172 g vs 337±165 g; P<0.001) and %fat (12.9±4.4% vs 9.9±4%; P<0.001) were significantly higher and fat-free mass (2681±348 g vs 2969±375 g; P<0.001) significantly lower than those by DXA. Fat-free mass estimates showed greater consistency in the level of agreement between the techniques compared with fat and %fat estimates where the differences between methods were less predictable.
  
  
  
  Although ADP and DXA body composition estimates are highly correlated in neonates, significant differences are observed between the techniques. This is particularly relevant for fat mass and %fat estimates, where differences are highly variable between methods. Further investigation is needed to minimise inter-method differences to ensure accurate and comparable assessment of body composition at birth and across longitudinal study follow-up.
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: S V
authors.initials: SV
authors.lastname: Wrottesley
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|Wits RHI, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: P T
authors.initials: PT
authors.lastname: Pisa
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: L K
authors.initials: LK
authors.lastname: Micklesfield
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: J M
authors.initials: JM
authors.lastname: Pettifor
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: S A
authors.initials: SA
authors.lastname: Norris
mesh_terms: D015502:Absorptiometry, Photon; D001823:Body Composition; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009751:Nutritional Requirements; D010991:Plethysmography; D015203:Reproducibility of Results; D013019:South Africa