Validation of DXA Body Composition Estimates in Obese Men and Women

Abstract

The aim of this study was to determine the accuracy of dual‐energy X‐ray absorptiometry (DXA)‐derived percentage fat estimates in obese adults by using four‐compartment (4C) values as criterion measures. Differences between methods were also investigated in relation to the influence of fat‐free mass (FFM) hydration and various anthropometric measurements. Six women and eight men (age 22–54 years, BMI 28.7–39.9 kg/m2, 4C percent body fat (%BF) 31.3–52.6%) had relative body fat (%BF) determined via DXA and a 4C method that incorporated measures of body density (BD), total body water (TBW), and bone mineral mass (BMM) via underwater weighing, deuterium dilution, and DXA, respectively. Anthropometric measurements were also undertaken: height, waist and gluteal girth, and anterior‐posterior (A‐P) chest depth. Values for both methods were significantly correlated (r2 = 0.894) and no significant difference (P = 0.57) was detected between the means (DXA = 41.1%BF, 4C = 41.5%BF). The slope and intercept for the regression line were not significantly different (P > 0.05) from 1 and 0, respectively. Although both methods were significantly correlated, intraindividual differences between the methods were sizable (4C‐DXA, range = −3.04 to 4.01%BF) and significantly correlated with tissue thickness (chest depth) or most surrogates of tissue thickness (body mass, BMI, waist girth) but not FFM hydration and gluteal girth. DXA provided cross‐sectional %BF data for obese adults without bias. However, individual data are associated with large prediction errors (±4.2%BF). This error appears to be associated with tissue thickness indicating that the DXA device used may not be able to accurately account for beam hardening in obese cohorts.

Sarcopenia, Relative Sarcopenia and Excess Adiposity in Chronic Kidney Disease

“…In addition to the biases raised above related to metrics of adiposity, the determination of lean mass by DXA can confounded by an excess of extracellular fluid (often, but not always large enough to result in overt edema) resulting in an over-estimate of lean (body cell) mass in some persons with CKD in whom magnetic resonance imaging would be more accurate. While DXA is quite accurate at the assessment of fat mass, [13,14] it is not as simple to apply broadly across the population as is body weight or waist circumference, and is more costly. Kidney Disease Improving Global Outcomes (KDIGO) guidelines now recommend the use of DXA in CKD to assess bone mineral density, so it is possible full body DXA could also be performed in the future including T and Z scores of ALMI adjusted for FMI on clinical reports.…”

“…[12] CKD stages were defined as follows: Stage 1+ 2 as eGFR ≥ 60 ml/min/1.73m 2 without albuminuria, stage 1A+2A as eGFR ≥ 60 ml/min/1.73m 2 with albuminuria, stage 3a = 45-59 ml/min/1.73m 2 , stage 3b = 30-44 ml/min/1.73m 2 , stage 4 = 15-29 ml/min/1.73m 2 , and stage 5 as <15 ml/min/1.73m 2 . Whole body DXA measures of fat mass and fat free mass have been validated and correlate highly with criterion methods [13,14] and were acquired using Hologic QDR 4500A fan-beam densitometers (Hologic, Inc, Bedford, MA). DXA exclusion criteria included pregnancy, weight >300 pounds (136 kg, due to the weight limit of the scanner), height >77 inches (195 cm), recent nuclear medicine scan or exposure to radioactive contrast.…”

Osteoporosis in Chronic Hepatitis C Virus with Advanced Liver Fibrosis

“…Two kinds of explorations following standard criteria were performed: a specific bone densitometric study of hip and lumbar spine, in order to record Z and T scores [11] . Because there exists the possibility of ambiguity when attempting to achieve accuracy within dual-energy X-ray absorptiometry (DXA) [12,13] , we used a simple method of body mass index (BMI) to assess body composition. BMI was defined as weight (kilograms) divided by height (meters) squared.…”

Fat and Bone: Where are We Now?

“…DXA remains the gold-standard clinical means of assessing skeletal parameters [8,9], although challenges in interpreting DXA in relation to body size and proportions [10], particularly in obese children [2], and tissue thickness and distribution in [11,12] have called into question the accuracy of assessing bone mass and density in relation to increasing adiposity. At the limits of in vivo scanning resolutions, HR-pQCT provides a detailed view of trabecular and cortical microarchitecture but is limited to the distal extremities and may not reflect skeletal changes elsewhere in the skeleton.…”