Validation of fan beam dual energy x ray absorptiometry for body composition assessment in adults aged 18-45 years.

Abstract

Pencil beam dual energy x ray absorptiometry (DXA) has been shown to provide valid estimates of body fat (%BF), but DXA fan beam technology has not been adequately tested to determine its validity. To compare %BF estimated from fan beam DXA with %BF determined using two and three compartment (2C, 3C) models. Men (n = 25) and women (n = 31), aged 18-41 years, participated in the study. Body density, from hydrostatic weighing, was used in the 2C estimate of %BF; DXA was used to determine bone mineral content (BMC) for the 3C estimate of %BF calculated using body density and BMC (3C(BMC)). DXA was also used to determine %BF. Analysis of variance was used to test for significant differences in %BF between sexes and among methods. Women were significantly shorter, weighed less, had less fat free mass, and a higher %BF than men. No significant differences were found among methods (2C, 3C(BMC), DXA) for determination of %BF in either sex. Although not significant, Bland-Altman plots showed that DXA gave higher values for %BF than the 2C and 3C(BMC) methods. DXA determination of %BF was not different from that of the 2C and 3C(BMC) models in this group of young adults. However, to validate fan beam DXA fully as a method for body composition assessment in a wide range of individuals and populations, comparisons are needed that use a 4C model with a measure of total body water and BMC.