Total Body Water Prediction Equations Research Articles

Development and validation of impedance-based equations for the prediction of total body water and fat free mass in children aged 8 to 11 years

Introduction et but de l’etude Accuracy of the impedance analysis depends on population-specific prediction equations. The aim of this study was to propose new prediction equations to estimate body composition using impedance analysis for healthy Tunisian children and validate them using the deuterium oxide dilution (D2O) technique. Materiel et methodes The body composition was estimated by the Tanita impedance analyzer. The validity of this system was investigated in 134 school children aged between 8 and 11 years. The validity of other published equations was also tested in our sample. Total body water (TBW) and Fat Free Mass (FFM) were determined using the D 2O technique. Participants were divided equally into development (n = 67) and validation groups (n = 67) to develop prediction equation using linear regression models. Resultats et analyse statistique The comparison between body composition obtained by Tanita system and by D2O technique illustrated a significant difference (P O technique, the impedance analysis underestimates fat mass and overestimates FFM and TBW. The prediction equations for TBW and FFM were developed with sex, age, weight and resistance index as possible predictor variables . The selected equations presented the highest adjusted coefficient of determination (R 2), the lowest standard error of the estimate (SEE) value and the lowest P values. The pure error was 1.263 for the TBW equation and 1.646 for the FFM. The Bland Altman plot illustrated the good level of concordance between the TBW and FFM predicted by the new equations and measured by isotope dilution. Conclusion Our study provides valid prediction equations for estimation of TBW, FFM from impedance analysis measures for Tunisian children. These equations are applicable to children aged between 8 and 11 years.

Development and validation of impedance-based equations for the prediction of total body water and fat-free mass in children aged 8–11 years

Accuracy of impedance analysis depends on population-specific prediction equations. The aim of this study was to propose new prediction equations to estimate body composition using impedance analysis for healthy Tunisian children and validate them using the deuterium oxide dilution (D2O) technique. Body composition was estimated by the Tanita impedance analyzer. The validity of this system was investigated in 134 school children aged between 8 and 11 years. The validity of other published equations was also tested in our sample. Total body water (TBW) and Fat-Free Mass (FFM) were determined using the D2O technique. Participants were divided equally into development (n=67) and validation groups (n=67) to develop prediction equation using linear regression models. The comparison between body composition obtained by Tanita system and by D2O technique illustrated a significant difference (p<0.01). Compared to D2O technique, Tanita impedance analysis underestimates fat mass and overestimates FFM and TBW. The prediction equations for TBW and FFM were developed with sex, age, weight and resistance index as possible predictor variables. The selected equations presented the highest adjusted coefficient of determination (R2), the lowest standard error of the estimate (SEE) value and the lowest p-values. The pure error was 1.263 for the TBW equation and 1.646 for the FFM. The Bland Altman plot illustrated the good level of concordance between the TBW and FFM predicted by the new equations and measured by isotope dilution. Our study provides valid prediction equations for estimation of TBW, FFM from impedance analysis measures for Tunisian children. These equations are applicable to children aged between 8 and 11 years.

Validation of anthropometric and bioelectrical impedance analysis (BIA) equations to predict total body water in a group of Cameroonian preschool children using deuterium dilution method

BackgroundLittle information is available on the validity of anthropometry or impedance-based equations for prediction of total body water (TBW) in African children. This study was designed to validate and develop equations to predict total body water in Cameroonian children.MethodsTBW was measured by deuterium dilution in 102 children between 24 and 60 months of age and compared with the ones predicted by 5 anthropometric and 7 BIA equations. Multiple linear regression analysis was used to develop prediction equations for TBW from anthropometric parameters.ResultsUnacceptable discrepancies in the estimates of TBW at individual level were noted with all the equations tested. The following new anthropometry and BIA equations for the estimation of TBW were respectively developed: TBW = 6.488 + 0.434 × sex − 0.039 × age + 0.670 × weight − 0.081 × MUAC (cm) − 0.372 × BMI (adjusted R2 = 0.71, RMSE = 3.6), and TBW = −6.206 + 0.0037 × height2/Z − 0.041 × age + 0.265 × weight + 0.1214 × height (adjusted R2 = 0.68, RMSE = 1.4). The cross-validation procedures revealed that the predicted values of TBW compared with measured values are accurate at a group level.ConclusionThe current published anthropometric and BIA equations are invalid for the estimation of TBW in Cameroonian preschool children. The newly developed anthropometry or BIA prediction equations are valid for use in Cameroonian children aged 24–60 months.

Estimation of total body water from bioelectrical impedance spectroscopy in oncology outpatients receiving radiotherapy and agreement with three prediction equations

Bioelectrical impedance spectroscopy (BIS) may be more accurate in determining total body water (TBW) than bioelectrical impedance analysis (BIA). The present study compared the agreement between three TBW prediction equations developed using BIA and BIS-derived TBW in oncology outpatients. A cross-sectional, observational study was conducted in 37 outpatients receiving radiotherapy (27 males/10 females, aged 68.3 +/- 10.2 years). TBW was estimated by BIS (TBW(BIS)) and three BIA TBW prediction equations (TBW(ca-u): underweight cancer patients; TBW(ca-n): normal-weight cancer patients; and TBW(rad): patients receiving radiotherapy). Bland-Altman analyses determined agreement between methods. BIS-derived TBW using new resistivity constants was calculated. The mean +/- SD of TBW estimated by BIS was 39.8 +/- 8.3 L, which was significantly different from the prediction equations; TBW(rad) 35.1 +/- 7.9 L, TBW(ca-u) 33.1 +/- 7.5 L and TBW(ca-n) 32.3 +/- 7.3 L, (P < 0.001). Using new resistivity constants, TBW was 36.2 +/- 8.1 L but this still differed from the equations (P < 0.001). Bias between TBW(BIS) and that predicted by the equations was in the range 4.7-7.4 L or 1.1-3.9 L using new resistivity constants. TBW estimated by BIS cannot be directly compared with oncology-specific BIA equations, suggesting that BIS cannot be used at the group level in outpatients receiving radiotherapy. There was a reduced bias with BIS using new resistivity constants; however, further research should determine any advantage of BIS over BIA in this population.

Anthropometric Prediction of Total Body Water in Children Who Are on Pediatric Peritoneal Dialysis

Accurate estimation of total body water (TBW) is a critical component of dialysis prescription in peritoneal dialysis (PD). Gold-standard isotope dilution techniques are laborious and costly; therefore, anthropometric prediction equations that are based on height and weight are commonly used to estimate TBW. Equations have been established in healthy populations, but their validity is unclear in children who undergo PD, in whom altered states of hydration and other confounding alterations in normal physiology, particularly retarded growth and pubertal delay, may exist. TBW was measured by heavy water (H2O18 or D2O) dilution in 64 pediatric patients who were aged 1 mo to 23 yr and receiving chronic PD in the United States and Germany to establish and validate population-specific anthropometric TBW prediction equations and to compare the predictive power of these equations with formulas that have been established in healthy children. The best-fitting equations are as follows: For boys, TBW = 0.10 x (HtWt)0.68 - 0.37 x weight; for girls, TBW = 0.14 x (HtWt)0.64 - 0.35 x weight. The height x weight parameter also predicts body surface area (BSA). These equations can be simplified, with slightly less precision, to the following: For boys, TBW = 20.88 x BSA - 4.29; for girls, TBW = 16.92 x BSA - 1.81. TBW is predicted without systematic deviations and equally well in boys and girls, North American and European, obese and nonobese, growth-retarded and normally sized, and pre- and postpubertal children. In contrast, previous anthropometric equations that were derived from healthy children systematically overpredicted TBW and were less precise in this pediatric PD population. In summary, a new set of anthropometric TBW prediction equations that are suited specifically for use in pediatric PD patients have been provided.

Total body water volume for white children and adolescents and anthropometric prediction equations: The Fels Longitudinal Study

There are few studies of total body water (TBW) volume in children. Such studies are needed, as are new prediction equations for the clinical management of children with renal insufficiency and those receiving dialysis. Mixed longitudinal data were from 124 white boys and 116 white girls 8 to 20 years of age. TBW volume was measured by deuterium nuclear magnetic resonance spectroscopy, and random effects models were used to determine patterns of change over time. Sex-specific TBW prediction equations were developed using regression analysis. Boys had significantly greater (P < 0.05) mean TBW volumes than girls at all but 3 ages. TBW was significantly (P < 0.05) associated with age and maturation in the boys and the girls. In boys, mean TBW/WT varied from 0.55 to 0.59, while in the girls the mean declined from 0.53 to 0.49 by 16 years of age. Boys had significantly larger means for TBW/WT than girls, who had a significant, slight negative trend with age. The prediction equations were TBW = -25.87 + 0.23 (stature) + 0.37 (weight) for boys and TBW =-14.77 + 0.18 (stature) + 0.25 (weight) for girls. Means are provided for TBW in white children from 8 to 20 years of age, whose average fatness affected the percentage of TBW in body weight. These updated TBW prediction equations perform better than those available from the past.

Estimation of total body water from foot‐to‐foot bioelectrical impedance analysis in patients with cancer cachexia – agreement between three prediction methods and deuterium oxide dilution

Bioelectrical impedance analysis (BIA) is a useful bedside measure to estimate total body water (TBW). The aim of this study was to determine the agreement between three equations for the prediction of TBW using BIA against the criterion method, deuterium oxide dilution, in patients with cancer cachexia. Eighteen measurements of TBW using foot-to-foot BIA in seven outpatients with cancer cachexia (five male and two female, age 56.4 +/- 6.7 years) at an Australian hospital. Three prediction formulae were used to estimate TBW - TBW(ca-radiotherapy) developed in patients with cancer undergoing radiotherapy, TBW(ca-underweight) and TBW(ca-normal weight) developed in underweight and normal weight patients with cachexia. TBW was measured using the deuterium oxide dilution technique as the gold standard. Mean measured TBW was 39.5 +/- 6.0 L. There was no significant difference in measured TBW and estimates from prediction equations TBW(ca-underweight) and TBW(ca-radiotherapy). There was a significant difference in measured TBW and TBW(ca-normal weight). All prediction equations overestimated TBW in comparison with measured TBW. The smallest bias was observed with TBW(ca-underweight) (0.38 L). The limits of agreement are wide (>7.4 L) for each of the prediction equations compared with measured TBW. At a group level, TBW(ca-underweight) is the best predictor of measured TBW in patients with cancer cachexia. For an individual however, the limits of agreement are wide for all prediction equations and are unsuitable for use. Practitioners need to be aware of the limitations of using TBW prediction equations for individuals.

Validity of impedance-based equations for the prediction of total body water as measured by deuterium dilution in African women

Little information is available on the validity of simple and indirect body-composition methods in non-Western populations. Equations for predicting body composition are population-specific, and body composition differs between blacks and whites. We tested the hypothesis that the validity of equations for predicting total body water (TBW) from bioelectrical impedance analysis measurements is likely to depend on the racial background of the group from which the equations were derived. The hypothesis was tested by comparing, in 36 African women, TBW values measured by deuterium dilution with those predicted by 23 equations developed in white, African American, or African subjects. These cross-validations in our African sample were also compared, whenever possible, with results from other studies in black subjects. Errors in predicting TBW showed acceptable values (1.3-1.9 kg) in all cases, whereas a large range of bias (0.2-6.1 kg) was observed independently of the ethnic origin of the sample from which the equations were derived. Three equations (2 from whites and 1 from blacks) showed nonsignificant bias and could be used in Africans. In all other cases, we observed either an overestimation or underestimation of TBW with variable bias values, regardless of racial background, yielding no clear trend for validity as a function of ethnic origin. The findings of this cross-validation study emphasize the need for further fundamental research to explore the causes of the poor validity of TBW prediction equations across populations rather than the need to develop new prediction equations for use in Africa.

Body composition of children in south-western Nigeria: validation of bio-electrical impedance analysis.

Bio-electrical impedance analysis (BIA) is a non-invasive method of estimating body composition and has the potential to be useful in clinics and for nutrition and health-related research in Africa. We sought to validate BIA for use among a Yoruba population in south-western Nigeria and to use BIA to assess the body composition of a healthy cohort of children. Total body water (TBW) was measured in 92 individuals (53 adults and 39 children) using deuterium dilution; height, weight and resistance were measured by BIA. Multiple regression analysis was used to develop prediction equations for TBW among children only or among all participants. Independent covariates tested in the regression models included the impedance index (height(2)/resistance), weight, age and gender with TBW as the dependent variable. Depending on the model used, between 97% (root MSE=0.7 kg ) and 99% (root MSE=0.7 kg) of the variance observed in TBW could be explained by the impedance index, weight and/or gender; age, however, was not significant in any model. In a separate cohort of 69 children, 5-8 years old, anthropometrics were measured and TBW was estimated using the developed equations. Body composition data are presented by gender and age group. BIA was validated for use among Nigerian children and adults and provides a potentially important tool for research.

Development of bioelectrical impedance analysis prediction equations for body composition with the use of a multicomponent model for use in epidemiologic surveys

Previous studies to develop and validate bioelectrical impedance analysis (BIA) equations to predict body composition were limited by small sample sizes, sex specificity, and reliance on reference methods that use a 2-component model. This study was designed to develop sex-specific BIA equations to predict total body water (TBW) and fat-free mass (FFM) with the use of a multicomponent model for children and adults. Data from 5 centers were pooled to create a sample of 1474 whites and 355 blacks aged 12-94 y. TBW was measured by dilution, and FFM was estimated with a multicomponent model based on densitometry, isotope dilution, and dual-energy X-ray absorptiometry. The final race-combined TBW prediction equations included stature(2)/resistance and body weight (R(2) = 0.84 and 0.79 and root mean square errors of 3.8 and 2.6 L for males and females, respectively; CV: 8%) and tended to underpredict TBW in black males (2.0 L) and females (1.4 L) and to overpredict TBW in white males (0.5 L) and females (0.3 L). The race-combined FFM prediction equations contained the same independent variables (R(2) = 0.90 and 0.83 and root mean square errors of 3.9 and 2.9 kg for males and females, respectively; CV: approximately 6%) and tended to underpredict FFM in black males (2.1 kg) and females (1.6 kg) and to overpredict FFM in white males (0.4 kg) and females (0.3 kg). These equations have excellent precision and are recommended for use in epidemiologic studies to describe normal levels of body composition.

Total body water reference values and prediction equations for adults

The clinical interpretation of total body water (TBW) necessitates the availability of timely comparative reference data. The prediction of TBW volume in renal disease is critical in order to prescribe and monitor the dose of dialysis in the determination of Kt/V. In clinical practice, urea distribution (V) is commonly predicted from anthropometric equations that are several decades old and for white patients only. This article presents new reference values and prediction equations for TBW from anthropometry for white and black adults. The study sample included four data sets, two from Ohio and one each from New Mexico and New York, for a total of 604 white men, 128 black men, 772 white women, and 191 black women who were 18 to 90 years of age. The TBW concentration was measured by the deuterium or tritium oxide dilution method, and body composition was measured with a Lunar DXA machine. An all-possible-subsets of regression was used to predict TBW. The accuracy of the selected equations was confirmed by cross-validation. Blacks had larger TBW means than whites at all age groups. The 75th TBW percentile for whites approximated the TBW median for blacks at most ages. The white men and black men and women had the largest TBW means ever reported for healthy individuals. The race- and sex-specific TBW prediction equations included age, weight, and stature, with body mass index (BMI) substituted for weight in the white men. The root mean square errors (RMSEs) and standard errors for the individual (SEIs) ranged from approximately 3.8 to 5.0 L for the men and from 3.3 to 3.6 L for the women. In both men and women, high values of TBW were associated with high levels of total body fat (TBF) and fat-free mass (FFM). : TBW in these healthy adults is relatively stable through a large portion of adulthood. There are significant race and sex differences in TBW. These accurate and precise equations for TBW provide a useful tool for the clinical prediction of TBW in renal disease for white and black adults. These are the first TBW prediction equations that are specific for blacks.

Validity of published prediction equations for body composition in high altitude Bolivian Aymara as evaluated by doubly labeled water

Total body water (TBW), fat-free mass (FFM), and fat as a percentage of body weight (fat%) were estimated by the doubly labeled water (DLW) technique in 23 healthy rural Bolivian subjects of a typical herding community of the high Andes. Using these values as the frame of reference, validation tests of several prediction equations for TBW and body density were made. Estimated values and errors for TBW, FFM, and fat% varied greatly with prediction equation. Among the prediction equations tested, however, three, Mellits and Cheek (1970; M&C), Durnin and Womersley (1974; D&W) and Conlisk et al. (1992; CNL), had a smaller bias and higher precision than others. Compared to the DLW method, the prediction errors of these equations for FFM and fat% as evaluated by the mean bias and the 95% limits of agreement were −0.7 ± 4.5 kg and 1.5 ± 10% (M&C), 0.9 ± 3.6 kg and −2.1 ± 8.5% (D&W), and 1.1 ± 3.6 kg and −2.7 ± 9.3% (CNL). For most practical purposes, these prediction errors for FFM as percentage of body weight may not be very important, but the errors in fat% may be serious. The interpretation of predicted data thus needs caution. In spite of differences in ethnic background and age range between the subjects and the samples on which the equations were developed, it is interesting that regression equations based on U.S., British and Guatemalan subjects also predicted the body composition of native Bolivian subjects with unexpectedly high precision. Am. J. Hum. Biol. 10:371–384, 1998. © 1998 Wiley-Liss, Inc.

Validity of published prediction equations for body composition in high altitude Bolivian Aymara as evaluated by doubly labeled water.

Total body water (TBW), fat-free mass (FFM), and fat as a percentage of body weight (fat%) were estimated by the doubly labeled water (DLW) technique in 23 healthy rural Bolivian subjects of a typical herding community of the high Andes. Using these values as the frame of reference, validation tests of several prediction equations for TBW and body density were made. Estimated values and errors for TBW, FFM, and fat% varied greatly with prediction equation. Among the prediction equations tested, however, three, Mellits and Cheek (1970; MC DW CNL), had a smaller bias and higher precision than others. Compared to the DLW method, the prediction errors of these equations for FFM and fat% as evaluated by the mean bias and the 95% limits of agreement were −0.7 ± 4.5 kg and 1.5 ± 10% (M&C), 0.9 ± 3.6 kg and −2.1 ± 8.5% (D&W), and 1.1 ± 3.6 kg and −2.7 ± 9.3% (CNL). For most practical purposes, these prediction errors for FFM as percentage of body weight may not be very important, but the errors in fat% may be serious. The interpretation of predicted data thus needs caution. In spite of differences in ethnic background and age range between the subjects and the samples on which the equations were developed, it is interesting that regression equations based on U.S., British and Guatemalan subjects also predicted the body composition of native Bolivian subjects with unexpectedly high precision. Am. J. Hum. Biol. 10:371–384, 1998. © 1998 Wiley-Liss, Inc.

Prediction of total body water in Indian men from anthropometry and bioelectrical impedance using deuterium dilution as reference

Total body water (TBW) obtained by deuterium dilution (TBW D ) in 45 adult Indian males of low body mass index was compared with values obtained from bioelectrical impedance (TBW Imp ) and two anthropometry-based prediction equations. Bioelectrical impedance significantly underestimated TBW when compared with deuterium dilution, by 2·75 SD 2·86 kg. Comparisons of the anthropometry-based prediction equations demonstrated that TBW was overestimated by 0·87 SD 2·49 kg, and 2·47 SD 2·57 kg, respectively. Since all parameters in the bioelectrical impedance method were standardized, the difference in the values could have been because of the equation used. Therefore, a fresh equation for the measurement of TBW by the bioelectrical impedance method was derived using the variables of height 2 /impedance and weight. New prediction equations for TBW were also derived based on anthropometric variables of weight and height. Body weight has the greatest influence in the prediction equations for TBW, and the equation derived was TBW (kg) = 0·533 × body weight (kg) + 3·77, SEE = 2·4 kg. Using height 2 /impedance gave the relationship: TBW (kg) = 0·568 body weight - 0·04 height 2 /impedance + 4·35, SEE = 1·9 kg.

Total body water volumes for adult males and females estimated from simple anthropometric measurements

Individual total body water volumes for 458 adult males and 265 adult females obtained from dilution studies, together with their height, weight, and age have been selected from the literature. These values were used to derive total body water prediction equations for adults of any age. The equations that gave the best fit were for males: formula (see text) and for females: formula (see text). Numerous other linear regression equations to predict total body water from anthropometric measurements have been reported in the literature. Most apply only to restricted age groups. These, and the equations from the present study were tested on completely independent data. In all cases the equations from the present study gave the best overall results, though for women one equation designed for a specific age group, gave for that age group a marginally better fit.