title: Use of air displacement plethysmography in the determination of percentage of fat mass in african american children.
abstract: The purpose of this study was to determine the ability of air displacement plethysmography (ADP) to estimate percentage of fat mass (%FM) in African American children. %FM was determined in 21 boys and 13 girls (11.0 +/- 1.4 y, 18.6 +/- 4.2 kg/m(2) [mean +/- SD]) by ADP (using six published densitometric equations) and dual-energy x-ray absorptiometry (DXA). Measures were done within 2 h of one another, in random order. Regardless of equation, %FM(ADP) was significantly correlated with %FM(DXA) (R(2) = 0.67-0.71, all p < 0.001). %FM(ADP) using the equation of Siri (%FM(ADP-Siri) 20.3 +/- 9.0) agreed most closely with %FM(DXA) (20.0 +/- 10.2, difference p = 0.729). Together, surface area artifact and bone mineral content per unit of bone-free fat-free mass accounted for 29% of the variance in the residual between methods. The correlation between %FM(ADP-Siri) and %FM(DXA) was not significant for those <35 kg (n = 10; R(2) = 0.084, p = 0.417). There was a trend toward %FM(ADP-Siri) underestimating %FM(DXA) in girls (-1.46 +/- 3.0%FM; p = 0.103) but not in boys (1.43 +/- 6.4%FM; p = 0.315). Predicted lung volume was 40.1% higher than measured lung volume (p < 0.001). %FM(ADP-Siri) determined using predicted lung volume was 23.5 +/- 8.9, higher than that using measured lung volume (p < 0.001) and higher than %FM(DXA) (p = 0.001). We conclude that in 9- to 14-y-old African American children and provided lung volume is measured, %FM using ADP with Siri's equation approximates that obtained by DXA. Body composition results determined by ADP in children <35 kg should be interpreted with caution.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center,, Nashville, TN 37232-2279, USA.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Buchholz
authors.forename: Karen M
authors.initials: KM
authors.lastname: Majchrzak
authors.forename: Kong Y
authors.initials: KY
authors.lastname: Chen
authors.forename: Sadhna M
authors.initials: SM
authors.lastname: Shankar
authors.forename: Maciej S
authors.initials: MS
authors.lastname: Buchowski
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D001741:Black or African American; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D009765:Obesity / Q000473:pathology*; D010991:Plethysmography / Q000379:methods* / Q000592:standards; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012737:Sex Factors