Validation of dual-energy x-ray absorptiometry and foot-foot impedance against deuterium dilution measures of fatness in children.
OBJECTIVE
To determine the validity of estimation of body fatness by dual-energy x-ray absorptiometry (DXA) and foot-foot bio-electrical impedance (BIA).


METHODS
In 176, 11-12-year-olds (84 boys; 92 girls) body fatness was measured using total body water (TBW), derived from deuterium oxide dilution space. Body fatness was also estimated from DXA and BIA. Methods were compared by regression and by Bland-Altman analysis using TBW measures as the reference.


RESULTS
In boys, mean fat mass from TBW was 9.8 kg (standard deviation, SD=6.1); bias by DXA estimated fat mass was +0.9 kg (limits of agreement -2.2 to +4.1) and bias for BIA was -5.2 kg (limits of agreement +0.5 to -10.8). In boys, regression analysis indicated significant differences in slope (p<0.001) for DXA, and both slope (p < 0.001) and intercept (p < 0.001) for BIA. In girls, mean fat mass from TBW was 12.1 kg (SD 7.7); bias for DXA was +1.2 kg (limits of agreement -1.9 to +5.1) and bias for BIA was -0.2 kg (limits of agreement -5.4 to +5.1). In girls, regression analysis indicated significant differences for slope and intercept (p<0.001 in all cases) for both DXA and BIA.


CONCLUSIONS
Errors in estimation of fat mass using BIA and DXA can be very large, and the direction of error can differ between the sexes.
Reilly
John J
JJ
University of Glasgow Division of Developmental Medicine, Faculty of Medicine, Yorkhill Hospitals, Glasgow, Scotland. jjr2y@clinmed.gla.ac.uk
Gerasimidis
Kostas
K
Paparacleous
Natasa
N
Sherriff
Andrea
A
Carmichael
Amanda
A
Ness
Andrew R
AR
Wells
Jonathan C
JC
D015502:Absorptiometry, Photon; D050154:Adiposity; D015992:Body Mass Index; D002648:Child; D017666:Deuterium Oxide; D017097:Electric Impedance; D004739:England; D005260:Female; D005528:Foot; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009765:Obesity / Q000175:diagnosis* / Q000503:physiopathology; D050177:Overweight / Q000175:diagnosis* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011865:Radioisotope Dilution Technique; D012044:Regression Analysis; D015203:Reproducibility of Results; D012737:Sex Factors
D017666:Deuterium Oxide