Prediction of fat-free mass by bioelectrical impedance analysis in older adults from developing countries: a cross-validation study using the deuterium dilution method.
OBJECTIVE
Several limitations of published bioelectrical impedance analysis (BIA) equations have been reported. The aims were to develop in a multiethnic, elderly population a new prediction equation and cross-validate it along with some published BIA equations for estimating fat-free mass using deuterium oxide dilution as the reference method.


METHODS
Cross-sectional study of elderly from five developing countries.


METHODS
Total body water (TBW) measured by deuterium dilution was used to determine fat-free mass (FFM) in 383 subjects. Anthropometric and BIA variables were also measured. Only 377 subjects were included for the analysis, randomly divided into development and cross-validation groups after stratified by gender. Stepwise model selection was used to generate the model and Bland Altman analysis was used to test agreement.


RESULTS
FFM = 2.95 - 3.89 (Gender) + 0.514 (Ht2/Z) + 0.090 (Waist) + 0.156 (Body weight). The model fit parameters were an R2, total F-Ratio, and the SEE of 0.88, 314.3, and 3.3, respectively. None of the published BIA equations met the criteria for agreement. The new BIA equation underestimated FFM by just 0.3 kg in the cross-validation sample. The mean of the difference between FFM by TBW and the new BIA equation were not significantly different; 95% of the differences were between the limits of agreement of -6.3 to 6.9 kg of FFM. There was no significant association between the mean of the differences and their averages (r= 0.008 and p= 0.2).


CONCLUSIONS
This new BIA equation offers a valid option compared with some of the current published BIA equations to estimate FFM in elderly subjects from five developing countries.
Aleman-Mateo
H
H
Departamento de Nutricion y Metabolismo. Coordinacion de Nutricion. Centro de Investigacion en Alimentacion y Desarrollo, A.C. Carretera a La Victoria km. 0.6 Hermosillo, Sonora. Apdo. Postal 1735. C.P. 83000. helio@ciad.mx
Rush
E
E
Esparza-Romero
J
J
Ferriolli
E
E
Ramirez-Zea
M
M
Bour
A
A
Yuchingtat
G
G
Ndour
R
R
Mokhtar
N
N
Valencia
M E
ME
Schoeller
D A
DA
D000273:Adipose Tissue / Q000502:physiology; D000368:Aged; D000704:Analysis of Variance; D001823:Body Composition / Q000502:physiology*; D001834:Body Water / Q000378:metabolism; D003430:Cross-Sectional Studies; D017666:Deuterium Oxide; D003906:Developing Countries; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D009765:Obesity / Q000175:diagnosis*; D011237:Predictive Value of Tests
D017666:Deuterium Oxide