Validation of rapid 4-component body composition assessment with the use of dual-energy X-ray absorptiometry and bioelectrical impedance analysis - PubMed (original) (raw)

Validation of rapid 4-component body composition assessment with the use of dual-energy X-ray absorptiometry and bioelectrical impedance analysis

Bennett K Ng et al. Am J Clin Nutr. 2018.

Erratum in

Abstract

Background: The 4-component (4C) model is a criterion method for human body composition that separates the body into fat, water, mineral, and protein, but requires 4 measurements with significant cost and time requirements that preclude wide clinical use. A simplified model integrating only 2 measurements-dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA)-and 10 min of patient time has been proposed.

Objective: We aimed to validate a rapid, simplified 4C DXA + BIA body composition model in a clinical population.

Design: This was a cross-sectional observational study of 31 healthy adults. Participants underwent whole-body DXA, segmental BIA, air displacement plethysmography (ADP), and total body water (TBW) measurement by deuterium (D2O) dilution. 4C composition was calculated through the use of the Lohman model [DXA mineral mass, D2O TBW, ADP body volume (BV), scale weight] and the simplified model (DXA mineral mass and BV, BIA TBW, scale weight). Accuracy of percentage of fat (%Fat) and protein measurements was assessed via linear regression. Test-retest precision was calculated with the use of duplicate DXA and BIA measurements.

Results: Of 31 participants, 23 were included in the analysis. TBWBIA showed good test-retest precision (%CV = 5.2 raw; 1.1 after outlier removal) and high accuracy to TBWD2O [TBWD2O = 0.956*TBWBIA, R2= 0.92, root mean squared error (RMSE) = 2.2 kg]. %Fat estimates from DXA, ADP, D2O, and BIA all showed high correlation with the Lohman model. However, only the 4C simplified model provides high accuracy for both %Fat (R2 = 0.96, RMSE = 2.33) and protein mass (R2= 0.76, RMSE = 1.8 kg). %Fat precision from 4C DXA + BIA was comparable with DXA (root mean square-SD = 0.8 and 0.6 percentage units, respectively).

Conclusions: This work validates a simplified 4C method that measures fat, water, mineral, and protein in a 10-min clinic visit. This model has broad clinical application to monitor many conditions including over/dehydration, malnutrition, obesity, sarcopenia, and cachexia.

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Figures

FIGURE 1

FIGURE 1

Linear regression between BV measurements from DXA and ADP (n = 23). High correlation was observed, although a slope significantly different from 1 was detected. These data were used to determine a linear correction equation for BV from DXA: BVADP = 0.993 BVDXA (95% CI: 0.990, 0.996). The dashed line is the line of identity. ADP, air displacement plethysmography; BV, body volume; DXA, dual-energy X-ray absorptiometry; RMSE, root mean squared error.

FIGURE 2

FIGURE 2

Linear regression between TBW measurements from BIA and D2O (n = 23). High correlation was observed, although a slope significantly different from 1 was detected. These data were used to determine a linear correction equation for TBW from BIA: TBWD2O = 0.956 TBWBIA (95% CI: 0.932, 0.979). The dashed line is the line of identity. BIA, bioelectrical impedance analysis; D2O, deuterium; RMSE, root mean squared error; TBW, total body water.

FIGURE 3

FIGURE 3

Linear regression between whole-body %Fat from the 2- and 3-component and 4C body composition assessment methods in this study and the reference 4C Lohman model (n = 23). “n.s.” indicates that the regression intercept was nonsignificant (_P_> 0.05) and set to 0. ADP, air displacement plethysmography; BIA, bioelectrical impedance analysis; DXA, dual-energy X-ray absorptiometry; D2O, deuterium; RMSE, root mean squared error; 4C, 4-component; %Fat, percentage of fat.

FIGURE 4

FIGURE 4

Linear regression of whole-body 4C residual protein measured by the DXA + BIA method compared with the Lohman reference method (n = 23). The equation for the line of best fit is ProtDXA+BIA 4C = 0.99 ProtLohman 4C (95% CI: 0.93, 1.05). The dashed line is the line of identity. BIA, bioelectrical impedance analysis; DXA, dual-energy X-ray absorptiometry; RMSE, root mean squared error; 4C, 4-component.

FIGURE 5

FIGURE 5

Histograms of FFM hydration (defined as TBW divided by FFM from DXA) (n = 23). More variance was observed with the use of BIA for TBW than with the use of D2O for TBW. The observed range of hydration values extends beyond physiologic bounds for healthy adults in the sample; definition of thresholds on plausible hydration levels may provide criteria to validate BIA TBW measurements. BIA, bioelectrical impedance analysis; DXA, dual-energy X-ray absorptiometry; D2O, deuterium; FFM, fat-free mass; TBW, total body water.

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