Body composition following stem cell transplant: Comparison of bioimpedance and air-displacement plethysmography

ObjectiveThe aim of this study was to assess the agreement between detected changes in body composition determined by bioimpedance spectroscopy (BIS) and air-displacement plethysmography (ADP) among patients with cancer undergoing peripheral blood stem cell transplantation (PBSCT); and to assess the agreement of absolute values of BIS with ADP and dual energy x-ray (DXA).MethodsForty-four adult hematologic cancer patients undergoing PBSCT completed both BIS and ADP assessment at preadmission and at 3 mo after transplantation. A subsample (n = 11) was assessed by DXA at 3 mo after transplantation. Results were examined for the BIS instrument’s default setting and three alternative predictive equations from the literature. Agreement was assessed by the Bland-Altman limits of agreement analysis while correlation was examined using the Lin’s concordance correlation.ResultsChanges in body composition parameters assessed by BIS were comparable with those determined by ADP regardless of the predictive equations used. Bias of change in fat-free mass was clinically acceptable (all <1 kg), although limits of agreement were wide (more than ±6 kg). Overall, the BIS predictive equation accounting for body mass index performed the best. Absolute body composition parameters predicted by the alternative predictive equations agreed with DXA and ADP better than the BIS instrument’s default setting.ConclusionChanges predicted by BIS were similar to those determined by ADP on a group level; however, agreement of predicted changes at an individual level should be interpreted with caution due to wide limits of agreement.     

Need for optimal body composition data analysis using air-displacement plethysmography in children and adolescents

Air-displacement plethysmography (ADP) is now widely used for body composition measurement in pediatric populations. However, the manufacturer's software developed for adults leaves a potential bias for application in children and adolescents, and recent publications do not consistently use child-specific corrections. Therefore we analyzed child-specific ADP corrections with respect to quantity and etiology of bias compared with adult formulas. An optimal correction protocol is provided giving step-by-step instructions for calculations. In this study, 258 children and adolescents (143 girls and 115 boys ranging from 5 to 18 y) with a high prevalence of overweight or obesity (28.0% in girls and 22.6% in boys) were examined by ADP applying the manufacturer's software as well as published equations for child-specific corrections for surface area artifact (SAA), thoracic gas volume (TGV), and density of fat-free mass (FFM). Compared with child-specific equations for SAA, TGV, and density of FFM, the mean overestimation of the percentage of fat mass using the manufacturer's software was 10% in children and adolescents. Half of the bias derived from the use of Siri's equation not corrected for age-dependent differences in FFM density. An additional 3 and 2% of bias resulted from the application of adult equations for prediction of SAA and TGV, respectively. Different child-specific equations used to predict TGV did not differ in the percentage of fat mass. We conclude that there is a need for child-specific equations in ADP raw data analysis considering SAA, TGV, and density of FFM.     

Evaluation of air-displacement plethysmography in children aged 5-7 years using a three-component model of body composition

The aim of the present study was to evaluate air-displacement plethysmography (ADP) in children aged 5-7 years. Body-composition measurements were obtained by ADP, (2)H dilution and anthropometry in twenty-eight children. Calculation of body volume by ADP was undertaken using adult and children's equations for predicting lung volume and surface area. Fat-free mass (FFM) was calculated using a three-component model. Measured FFM hydration was then compared with values from the reference child. Differences between measured and reference hydration were back-extrapolated, to calculate the error in ADP that would account for any disagreement. Propagation of error was used to distinguish the contributions of methodological precision and biological variability to total hydration variability. The use of children's equations influenced the results for lung volume but not surface area. The mean difference between measured and reference hydration was 0.6 (sd 1.7) % (P<0.10), equivalent to an error in body volume of 0.04 (sd 0.20) litres (P<0.30), and in percentage fat of 0.4 (sd 1.9) (P<0.28). The limits of agreement in individuals could be attributed to methodological precision and biological variability in hydration. It is concluded that accuracy of ADP was high for the whole group, with a mean bias of <0.5 % fat using the three-component model, and after taking into account biological variability in hydration, the limits of agreement were around +/-2 % fat in individuals. Paediatric rather than adult equations for lung volume estimation should be used.     

Body-composition assessment via air-displacement plethysmography in adults and children: a review

Laboratory-based body-composition techniques include hydrostatic weighing (HW), dual-energy X-ray absorptiometry (DXA), measurement of total body water (TBW) by isotope dilution, measurement of total body potassium, and multicompartment models. Although these reference methods are used routinely, each has inherent practical limitations. Whole-body air-displacement plethysmography is a new practical alternative to these more traditional body-composition methods. We reviewed the principal findings from studies published between December 1995 and August 2001 that compared the BOD POD method (Life Measurement, Inc, Concord, CA) with reference methods and summarized factors contributing to the different study findings. The average of the study means indicates that the BOD POD and HW agree within 1% body fat (BF) for adults and children, whereas the BOD POD and DXA agree within 1% BF for adults and 2% BF for children. Few studies have compared the BOD POD with multicompartment models; those that have suggest a similar average underestimation of approximate 2-3% BF by both the BOD POD and HW. Individual variations between 2-compartment models compared with DXA and 4 -compartment models are partly attributable to deviations from the assumed chemical composition of the body. Wide variations among study means, -4.0% to 1.9% BF for BOD POD - HW and -3.0% to 1.7% BF for BOD POD - DXA, are likely due in part to differences in laboratory equipment, study design, and subject characteristics and in some cases to failure to follow the manufacturer's recommended protocol. Wide intersubject variations between methods are partly attributed to technical precision and biological error but to a large extent remain unexplained. On the basis of this review, future research goals are suggested.     

Body composition predicted with a Bayesian network from simple variables

The relative contributions of fat-free mass (FFM) and fat mass (FM) to body weight are key indicators for several major public health issues. Predictive models could offer new insights into body composition analysis. A non-parametric equation derived from a probabilistic Bayesian network (BN) was established by including sex, age, body weight and height. We hypothesised that it would be possible to assess the body composition of any subject from easily accessible covariables by selecting an adjusted FFM value within a reference dual-energy X-ray absorptiometry (DXA) measurement database (1999-2004 National Health and Nutrition Examination Survey (NHANES), n 10?402). FM was directly calculated as body weight minus FFM. A French DXA database (n 1140) was used (1) to adjust the model parameters (n 380) and (2) to cross-validate the model responses (n 760). French subjects were significantly different from American NHANES subjects with respect to age, weight and FM. Despite this different population context, BN prediction was highly reliable. Correlations between BN predictions and DXA measurements were significant for FFM (R2 0·94, P?相似文献   

Changes in thoracic gas volume with air-displacement plethysmography after a weight loss program in overweight and obese women

OBJECTIVE: This study was designed to compare measured and predicted thoracic gas volume (V (TG)) after weight loss and to analyze the effect of body composition confounders such as waist circumference (WC) on measured V (TG) changes. DESIGN: Prospective intervention study. SETTING: Outpatient University Laboratory, Lisbon, Portugal. SUBJECTS: Eighty-five overweight and obese women (body mass index = 30.0+/-3.5 kg/m(2); age = 39.0+/-5.7 years) participating in a 16-month university-based weight control program designed to increase physical activity and improve diet. METHODS: Body weight (Wb), body volume (Vb), body density (Db), fat mass (FM), percent fat mass (%FM) and fat-free mass (FFM) were assessed by air-displacement plethysmography (ADP) at baseline and at post-intervention (16 months). The ADP assessment included a protocol to measure V (TG) and a software-based predicted V (TG). Dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1500) was also used to estimate FM, %FM and FFM. Maximal oxygen uptake (VO(2) max) was assessed with a modified Balke cardiopulmonary exercise testing protocol with a breath-by-breath gas analysis. RESULTS: Significant differences between the baseline and post-weight loss intervention were observed for body weight and composition (Vb, Db, %FM, FM and FFM), and measures of V (TG) (measured: Delta=0.2 l, P<0.001; predicted: Delta=0.01 l, P<0.010) variables. Measured V (TG) change was negatively associated with the change in the WC (P=0.008), controlling for VO(2) max and age (P=0.007, P=0.511 and P=0.331). Linear regression analysis results indicated that %FM and FM using the measured and predicted V (TG) explained 72 and 76%, and 86 and 90% respectively, of the variance in %FM and FM changes using dual-energy x-ray absorptiometry. CONCLUSIONS: After weight loss, measured V (TG) increased significantly, which was partially attributed to changes is an indicator of body fat distribution such as WC. Consequently, measured and predicted V (TG) should not be used interchangeably when tracking changes in body composition. The mechanisms relating the reduction of an upper body fat distribution with an increase measured V (TG) are worthy of future investigation.     

Body-composition assessment in infancy: air-displacement plethysmography compared with a reference 4-compartment model

BACKGROUND: A better understanding of the associations of early infant nutrition and growth with adult health requires accurate assessment of body composition in infancy. OBJECTIVE: This study evaluated the performance of an infant-sized air-displacement plethysmograph (PEA POD Infant Body Composition System) for the measurement of body composition in infants. DESIGN: Healthy infants (n = 49; age: 1.7-23.0 wk; weight: 2.7-7.1 kg) were examined with the PEA POD system. Reference values for percentage body fat (%BF) were obtained from a 4-compartment (4-C) body-composition model, which was based on measurements of total body water, bone mineral content, and total body potassium. RESULTS: Mean (+/- SD) reproducibility of %BF values obtained with the PEA POD system was 0.4 +/- 1.3%. Mean %BF obtained with the PEA POD system (16.9 +/- 6.5%) did not differ significantly from that obtained with the 4-C model (16.3 +/- 7.2%), and the regression between %BF for the 4-C model and that for the PEA POD system (R2 = 0.73, SEE = 3.7%BF) did not deviate significantly from the line of identity (y = x). CONCLUSIONS: The PEA POD system provided a reliable, accurate, and immediate assessment of %BF in infants. Because of its ease of use, good precision, minimum safety concerns, and bedside accessibility, the PEA POD system is highly suitable for monitoring changes in body composition during infant growth in both the research and clinical settings.     

TOBEC methodology for body composition assessment: a cross-validation study

The accuracy of prediction equations for estimating lean body mass (LBM) from total-body electrical conductivity (TOBEC) was examined by cross-validation. Two samples of adults, aged 18-35 yr, were drawn from separate geographic locations. LBM was determined by densitometry and TOBEC was measured with TOBEC II instrument. LBM and TOBEC were highly correlated in both samples (r = 0.96 and 0.97). Cross-validation of LBM prediction equations was accomplished by exchanging equations and comparing predicted LBM values. There was a mean difference of 0.974 kg LBM between the two equations (p less than 0.0001). Thus, data from 157 subjects were pooled and one equation was developed that incorporated height (cm), sex (males = 0, females = 1), and the zero-, first-, and second-order Fourier coefficients (FC0, FC1, and FC2) of the TOBEC phase value: LBM, kg = -36.410 + (-1.324 X sex) + (0.01185 X (FC1(0.5)xht)) + (12.347 X FC2(0.5)) + (0.0627 X FC0)-(0.9232 X FC2) This equation, developed from 157 subjects, accounted for 96% of the variability in LBM and had a standard error of estimate of 2.17 kg LBM.     

Comparison of air-displacement plethysmography with hydrostatic weighing and bioelectrical impedance analysis for the assessment of body composition in healthy adults

BACKGROUND: Over the past decade, considerable attention has been paid to accurately measuring body composition in diverse populations. Recently, the use of air-displacement plethysmography (AP) was proposed as an accurate, comfortable, and accessible method of body-composition analysis. OBJECTIVE: The purpose of this study was to compare measurements of percentage body fat (%BF) by AP and 2 other established techniques, hydrostatic weighing (HW) and bioelectrical impedance analysis (BIA), in adults. DESIGN: The sample consisted of healthy men (n = 23) and women (n = 24). %BF was measured by AP, HW, and BIA. RESULTS: In the total group, %BF(AP) (25.0+/-8.9%) was not significantly different from %BF(HW) (25.1+/-7.7%) or %BF(BIA) (23.9+/-7.7%), and %BF(AP) was significantly correlated with %BF(HW) (r = 0.944, P < 0.001) and with %BF(BIA) (r = 0.859, P < 0.01). Compared with HW, AP underestimated %BF in men (by -1.24+/-3.12%) but overestimated %BF in women (by 1.02+/-2.48%), indicating a significant sex effect (P < 0.05). The differences in estimation between AP and BIA and between BIA and HW were not significantly different between the sexes. CONCLUSION: AP is an accurate method for assessing body composition in healthy adults. Future studies should assess further the cause of the individual variations with this new method.     

Body composition in children and adults by air displacement plethysmography.

OBJECTIVES: Air displacement plethysmography (ADP) may provide a partial alternative to body density (Bd) and therefore body composition measurement compared to conventional hydrodensitometry (Hd) in children. As there are no evaluation studies of ADP in children, this study had a two-fold objective: to compare Bd estimates by ADP and Hd; and to compare fat estimates by both ADP and Hd to fat estimates by another reference method, dual energy X-ray absorptiometry (DXA). SETTING: Obesity Research Center, St. Luke's/Roosevelt Hospital, New York, USA. SUBJECTS: One hundred and twenty subjects (66 females/54 males) who ranged in age from 6-86 y and in body mass index (BMI, kg/m2) from 14.1-40.0 kg/m2 met study entry criteria. STUDY DESIGN: Cross-sectional study of healthy children (age < or = 19 y) and adult group for comparison to earlier studies. Each subject completed ADP, Hd, and DXA studies on the same day. Only subjects with subjectively-judged successful Hd studies were entered into the study cohort. RESULTS: There was a high correlation between Bd by ADP and Hd (Bd Hd = 0.11 + 0.896 x Bd ADP; r = 0.93, SEE = 0.008 g/cm3, P < 0.0001), although the regression line slope and intercept differed significantly from 1 and 0, respectively. Additional analyses localized a small-magnitude Bd bias in the child (n = 48) subgroup. Both ADP and Hd %fat estimates were highly correlated (r > 0.9, P < 0.0001) with %fat by DXA in child and adult subgroups. Bland-Altman analyses revealed no significant %fat bias by either ADP or Hd vs DXA in either children or adults, although a bias trend (P = 0.11) was detected in the child subgroup. CONCLUSION: With additional refinements, the air displacement plethysmography system has the potential of providing an accurate and practical method of quantifying body fat in children as it now does in adults.     

Body composition of African American and white children: a 2-year follow-up of the BAROC study

OBJECTIVE: To evaluate the 2-year changes in body composition of white and African American boys and girls. RESEARCH METHODS AND PROCEDURES: A total of 114 boys and girls ages 12 to 14 years with equal sex and ethnic distribution between African American and white races participated in measurements of body composition using DXA, underwater weighing (densitometry), skinfold thickness, corporal diameters, circumferences, isotope dilution (H(2)(18)O), and bioelectric impedance. RESULTS: Sixty-eight of the 114 children advanced from Tanner Stages 1 and 2 to Tanner Stages 3 to 5 over a 2-year period. More than 50% of the children were in the top 15th percentile according to normative data for body mass index but not for triceps skinfold. All measures except for percentage of fat, density, and four of the six skinfolds increased significantly during the 2 years, with no differences between races, genders, or fat group. The boys who advanced in Tanner Stage reduced their percentage of fat and a number of skinfolds and increased their lean body mass, but the girls did not. The percentage of water was significantly higher in the fatter children and declined significantly over 2 years. Most children remained in the same quartile of body fat, lean body mass, and bone mineral content over 2 years. DISCUSSION: The data are consistent with the hypothesis that over 2 years, growth is the major determinant of changing body composition, with body-fat group and sexual maturation being additional variables.     

Prediction of DXA-determined whole body fat from skinfolds: importance of including skinfolds from the thigh and calf in young, healthy men and women

OBJECTIVE: To investigate the relationship of percent body fat (%fat), assessed by dual energy-X-ray absorptiometry (DXA) or a four-compartment model, with upper body and lower limb skinfolds. DESIGN: Cross-sectional design involving forward stepwise and hierarchical multiple regression analyses to assess the relationship of %fat with skinfolds and a combination of four commonly used upper body skinfolds (biceps, triceps, subscapular and iliac crest) with the calf and thigh skinfolds. SETTING: University research laboratory. SUBJECTS: In all, 31 females, mean age 20.9 (+/-2.0) y, and 21 males, mean age 22.3 (+/-5.5) y volunteered for this study, which was approved by the Ethics Committee of the School of Sport, Health and Exercise Sciences, University of Wales, Bangor. MEASUREMENTS: %fat from DXA in both groups, and %fat from a four-compartment (water, bone mineral mass, fat and residual) model (%fat4C) in females only. Skinfolds were measured at the abdomen, iliac crest, biceps, triceps, subscapular, calf and thigh. RESULTS: All skinfolds were positively associated with DXA estimates of %fat (P < 0.01). In males and females, the thigh skinfold had the highest correlation with %fat. This was also observed when %fat4C was used as the criterion in females. Stepwise multiple regression analysis using %fatDXA as the criterion selected the thigh (R(2) = 0.82), calf (R(2) change 0.04) and iliac crest (R(2) change = 0.03) for females, and the thigh (R(2) = 0.79), iliac crest (R(2) change = 0.11) and abdomen (R(2) change = 0.03) for males (all P < 0.01). When %fat4C was used as the criterion in the females, only the thigh was selected as a significant predictor (R(2) = 0.76). Independent prediction factors were created from the sum of biceps, triceps, subscapular and iliac crest (sigma4skf) and from the sum of the thigh and calf (sigmathigh + calf). These factors were then entered into a hierarchical multiple linear regression analysis to predict percent fat. Order of entry was varied to allow the assessment of unique variance accounted for by each predictor. The sum of the thigh and calf explained more variance in %fatDXA than that explained by the sigma4skf alone, irrespective of the order of entry in both males and females. This was also observed when %fat4C was used as the criterion in the females. CONCLUSIONS: The results of this study confirm that lower body skinfolds are highly related to percent body fat in fit and healthy young men and women, and uphold current recommendations by the British Olympic Association to include the thigh skinfold with sigma4skf. Conventional use of the sigma4skf to estimate percent body fat is significantly enhanced by the inclusion of the thigh and calf skinfolds, either independently or in combination. In this group of males and females, the sum of the thigh and calf skinfolds accounted for the most variance in percent fat.     

Development and cross-validation of a prediction equation for estimating resting energy expenditure in healthy African-American and European-American women

OBJECTIVE: To develop, validate, and cross-validate a formula for predicting resting energy expenditure (REE) in African-American and European-American women. DESIGN: A cross-sectional study of REE in women. Participants were randomly assigned to one of two groups. One group served to develop and validate a new equation for predicting REE while the second was used to cross-validate the prediction equation. The accuracy of the equation was compared to several existing formulae. SETTING: University metabolic laboratory, Memphis, TN, USA. SUBJECTS: Healthy, premenopausal African-American and European-American women between 18 and 39 y of age. The validation sample included 239 women (age: 28.4 y, wt: 70.7 kg, body mass index (BMI): 25.2 kg/m(2), REE: 5840 kJ/day), while the cross-validation sample consisted of 232 women (age: 27.5 y, wt: 70.7 kg, BMI: 25.2 kg/m(2), REE: 5784 kJ/day). RESULTS: The prediction equation derived from the current sample, which included adjustments for ethnicity, was the only formula that demonstrated a high level of accuracy for predicting REE in both African-American and European-American women. The mean difference between REE predicted from the new formula and measured REE was 28 kJ/day (s.d.=668) for European-American women and 142 kJ/day (s.d.=584) for African-American women. CONCLUSIONS: Previous equations for predicting energy needs may not be appropriate for both African-American and European-American women due to ethnic differences in REE. A new equation that makes adjustments in predicted REE based on ethnicity is recommended for determining energy needs in these groups (Predicted REE (kJ/day)=616.93-14.9 (AGE (y))+35.12 (WT (kg))+19.83 (HT (cm))-271.88 (ETHNICITY: 1=African American; 0=European American)). SPONSORSHIP: Support for this study was provided by Grant #HL53261 from the National Heart, Lung, and Blood Institute.     

Body composition in children with bronchopulmonary dysplasia predicted from bioelectric impedance and anthropometric variables: comparison with a reference dual X-ray absorptiometry

Since children with bronchopulmonary dysplasia often suffer from malnutrition and growth failure, evaluation of body composition is a very important tool to nutritional support. The aim of this study was to compare assessment of fat-mass (FM) and fat-free mass (FFM), evaluated by bio-impedancemetry and anthropometry compared to dual-X-ray-absorptiometry (DXA) in children with bronchopulmonary dysplasia. PATIENTS: Seventy-one children, aged 4-8 years, with bronchopulmonary dysplasia were enrolled. METHODS: FM and FFM measured using anthropometry and bio-impedancemetry were compared to FM and FFM obtained by DXA using the Bland-Altman method. RESULTS: Both bio-impedancemetry and anthropometry gave good agreement with DXA to evaluate FM and FFM. Anthropometry method, in general, slightly under-estimated FM (mean difference: -0.02 kg, standard deviation: 0.99) and FFM (mean difference: -0.70 kg+/-1.72). Bio-impedancemetry method overestimated FM (mean difference: 0.34 kg+/-2.06) and underestimated FFM (mean difference: -1.24 kg+/-3.32). CONCLUSION: In children with bronchopulmonary dysplasia aged, 4-8 years, both anthropometry and bio-impedancemetry cannot be used to precisely evaluate body composition.     

Body composition assessment in adults with cystic fibrosis: comparison of dual-energy X-ray absorptiometry with skinfolds and bioelectrical impedance analysis

OBJECTIVE: We compared body composition measurement in adults with cystic fibrosis (CF) by using non-invasive methods (skinfold thicknesses and bioelectrical impedance analysis [BIA]) with dual-energy X-ray absorptiometry (DXA). METHODS: Seventy-six adults with CF (mean age 29.9 +/- 7.9 y, mean body mass index 21.5 +/- 2.5 kg/m(2)) were studied. Body composition was measured to calculate fat-free mass (FFM) using DXA, the sum of four skinfold thicknesses, and BIA (predictive equations of Lukaski and of Segal). RESULTS: Mean FFM values +/- standard deviation measured using DXA were 54.8 +/- 7.3 kg in men and 41.2 +/- 3.9 kg in women. Mean FFM values measured using BIA/Lukaski were 51.5 +/- 7.8 kg in men and 40.4 +/- 4.9 kg in women (P < 0.0005 for men, not significant for women for comparison with DXA). Mean FFM values measured using BIA/Segal were 54.2 +/- 7.5 kg for men and 44.1 +/- 5.9 kg for women (not significant for men, P < 0.0005 for women for comparison with DXA). Mean FFM values measured using skinfolds were significantly higher than those for FFM with DXA (57.2 +/- 7.2 kg in men, 43.3 +/- 4.3 kg in women, P < 0.0005 for comparison with DXA). The 95% limits of agreement with FFM using DXA were, for men and women, respectively, -8.3 to 1.7 kg and -6.4 to 4.8 kg for BIA/Lukaski, -4.8 to 3.6 kg and -3.1 to 8.9 kg for BIA/Segal, and -2.8 to 7.3 kg and -1.5 to 5.7 kg for skinfolds. CONCLUSION: This study suggests that skinfold thickness measurements and BIA will incorrectly estimate FFM in many adults with CF compared with DXA measurements of FFM. These methods have limited application in the assessment of body composition in individual adult patients with CF.     

Genetically predicted body composition in relation to cardiometabolic traits: a Mendelian randomization study

European Journal of Epidemiology - Fat mass and fat-free mass are found to be associated with different health outcomes in observational studies, but the underlying causality remains unclear. We...