ANTHROPOMETRICS DO NOT INFLUENCE DUAL X-RAY ABSORPTIOMETRY (DXA) MEASUREMENT OF FAT IN NORMAL TO OBESE ADULTS - A COMPARISON WITH IN-VIVO NEUTRON-ACTIVATION ANALYSIS (IVNA)
Ma. Marcus et al., ANTHROPOMETRICS DO NOT INFLUENCE DUAL X-RAY ABSORPTIOMETRY (DXA) MEASUREMENT OF FAT IN NORMAL TO OBESE ADULTS - A COMPARISON WITH IN-VIVO NEUTRON-ACTIVATION ANALYSIS (IVNA), Obesity research, 5(2), 1997, pp. 122-130
Dual-energy X-ray absorptiometry (DXA) is now a commonly used method f
or the determination of bone mineral status and body composition in hu
mans. The purposes of this study were to compare fat mass by in vivo n
eutron activation analysis (FM(IVNA)) with that by DXA (FM(DXA)) in an
anthropometrically heterogeneous sample of healthy adult men (n=33) a
nd women (n=36) (19 less than or equal to BMI less than or equal to 39
), and to determine whether differences in fat mass estimates between
the two methods (Delta FM) were attributable to subject anthropometry
as defined by several circumference (waist, iliac crest, thigh) and sk
infold thickness (umbilical, suprailiac, abdominal) measurements. No s
ignificant differences between FM(DXA) and FM(IVNA) were observed in m
en (p=0.46) or women (p=0.09). The two methods were very highly correl
ated in both sexes (women r(2)=0.97, p<0.001, men r(2)=0.91, p<0.001),
although the regression line for men was significantly different from
the line of identity (p=0.043), These results suggest modest trends t
oward underestimation of FM(DXA) in men when FM(IVNA)<18 kg, and overe
stimation in men when FM(IVNA)>18 kg. Delta FM (IVNA-DXA) was not sign
ificantly related to any combination of skinfold thicknesses and circu
mferences in either gender. Age explained 27% of the variance in Delta
FM for the men (p=0.008). Furthermore, Delta FM was not significantly
related to inter-method disparity in total-body bone mineral measurem
ents in men or women (p<0.05). The present study demonstrates strong c
orrelation in fat measurements between IVNA and DXA in men and women r
anging from normal to markedly obese. Correction for subject anthropom
etry does not significantly improve this relationship.