Development Of A Dxa-derived Body Volume Equation In Hispanic Adults For Administering In 4-compartment Models

Abstract

PURPOSE: The purpose of the current study was two-fold: 1) to develop a new dual energy X-ray absorptiometry (DXA)-derived body volume (BV) equation with the GE-Lunar Prodigy while utilizing underwater weighing (UWW) as a criterion and 2) cross-validate 4-compartment(4C) models when utilizing the new DXA-derived BV equation (4C-DXANICKERSON), Wilson DXA-derived BV equation (4C-DXAWILSON), and air displacement plethysmography (ADP)-derived BV (4C-ADP) in Hispanic adults. METHODS: 191 Hispanic adults (18-45yrs) participated in the current study. The development sample consisted of 60 females and 60 males whereas the cross-validation sample comprised of 41 females and 30 males. Criterion body fat percentage (BF%) and fat-free mass (FFM) were determined using a 4C model with UWW as a criterion for BV (4C-UWW). The new DXA-derived BV equation (Nickerson) was developed by linearly regressing UWW-derived BV with DXA fat mass (FM), lean mass (LM), and bone mineral content (BMC). 4C-DXANICKERSON, 4C-DXAWILSON, and 4C-ADP were compared against 4C-UWW in the cross-validation sample. RESULTS: The new DXA-derived BV equation (L) was generated in the development sample as follows: (FM/0.91) + (LM/1.06) + (BMC/16.95) + 0.268. 4C-DXANICKERSON, 4C-DXAWILSON, and 4C-ADP all produced similar mean values (BF%=21.04±5.99, 22.23±6.93, and 20.62±6.26%, respectively) when compared to 4C-UWW (21.29±6.14%) in Hispanic males (all p>0.05). 4C-DXANICKERSON also yielded similar BF% and FFM values as 4C-UWW when evaluating the constant error (CE) in Hispanic females (CE=-0.79% and 0.38kg; p=0.060 and 0.174, respectively). However, 4C-DXAWILSON produced significantly different BF% and FFM values (CE=3.22% and -2.20kg, respectively; both p<0.001). Additionally, 4C-DXAWILSON yielded significant proportional bias when estimating BF% (coefficient=0.226; p<0.001) whereas 4C-ADP produced significant proportional bias for BF% and FFM (coefficient=0.188 and -0.084; both p<0.05) when evaluated in Hispanic females. CONCLUSIONS: Current study findings demonstrate that 4C-DXANICKERSON is a valid measure of BV in Hispanics and is recommended for use in clinics where DXA is the main body composition assessment technique.