生物电阻抗法测量7～10岁儿童总体水含量和去脂体重的预测模型

目的利用生物电阻抗方法测量儿童的体成分,建立适合我国儿童体成分的预测方程。方法在北京市采用目的抽样法选取409名7～10岁的儿童（男生220名,女生189名）,测量身高和体重,采用生物电阻抗仪测量全身电阻抗和电容抗,采用单标水法测量的总体水（totalbodywater,TBW）和去脂体重（fat—freemass,FFM）作为标准,用多元线性逐步回归法建立回归方程,并采用纯误差和Bland—Altman分析法来判断预测方程的准确度。结果TBW的预测方程=-6．893＋0．410x性别（男：1,女=0）＋0．273×年龄（岁）＋0．174x体重（k）＋0．081×身高（cm）＋0．206x阻抗指数（cm2/Ω）（R2=0．90,均方根误差=1．2kg）;FFM的预测方程=-9．742＋0．784x性别（男=1,女=0）＋0．429x年龄（岁）＋0．227×体重（kg）＋0．104x身高（cm）＋0．269×阻抗指数（cm2／Ω）（R2=0．90,均方根误差=1．6kg）。TBW和FFM的预测值与测量值间差异均无统计学意义,纯误差分别是1．4、1．8kg。TBW和FFM的测量值与预测值的差值与均值之间存在显著正相关性（相关系数分别为0．24、0．23,P〈0．01）。不同BMI分组的测量值与预测值间差异均无统计学意义。结论推导的预测方程有较高的精确度和准确度,能有效准确地预测我国7～10岁儿童的体成分。     

Body composition estimated by bioelectrical impedance in the Swedish elderly. Development of population-based prediction equation and reference values of fat-free mass and body fat for 70- and 75-y olds

OBJECTIVE: To develop a bioelectrical impedance (BIA) prediction equation for fat-free mass (FFM(BIA)) and present reference values of FFM and body fat (BF) for healthy Swedish elderly from population-based representative samples. SUBJECTS: This study is based on 823 (344 males, 479 females) participants from two systematic samples of birth cohorts in G?teborg aged 70 (cohort H70V, 201 males and 299 females) and 75 (cohort NORA75, 143 males and 180 females). METHODS: Body composition was measured with BIA (BIA-101, RJL system, Detroit) in both cohorts and was estimated by a four-compartment (4C) model from total body water (TBW) and total body potassium (TBK) in a sub-sample of the NORA75 cohort. The FFM(BIA) was validated against the FFM from the 4C model (FFM(4C)). RESULTS: The FFM(BIA) correlated well with FFM(4C) (r=0.95, SEE=2.64 kg). The FFM(BIA) (kg) in 70-y-old males and females were 58.5+/-5.4 and 43.4+/-4.4, and for 75-y-old males and females were 56.1+/-4.7 and 42.5+/-4, respectively. The body fat in kg (FM) among 70-y-old males and females were 25.2+/-8.1 and 25.7+/-8.4, and for 75-y-old males and females were 21.7+/-7.1 and 22.8+7.2, respectively. The percent body fat (BF%) among 70-y-old males and females were 29.5+/-5.8 and 36.3+/-6.4, and for 75-y-old males and females were 27.3+/-6 and 34.1+/-6.1, respectively. CONCLUSION: The FFM, FM and BF% from this study might be used as reference values for Swedish elderly aged 70 and 75 y.     

Comparison of bioelectrical impedance prediction equations for fat-free mass in a population-based sample of 75 y olds: the NORA study

OBJECTIVE: We evaluated the performance of different prediction equations to estimate fat-free mass (FFM) from bioelectrical impedance analysis (BIA) in the elderly. METHODS: This study was based on 106 (51 male and 55 female) free-living 75-y-old subjects who participated in the G?teborg part of the Nordic Research on Ageing (NORA) study during 1991 and 1992. FFM predicted from BIA (FFM(GOT)) was validated against FFM estimated from measurements of total body water and total body potassium (FFM(REF)). FFM was calculated from BIA prediction equations for the elderly developed by Deurenberg et al. (FFM(WAG)) and Roubenoff et al. (FFM(FHS)). FFM also was calculated from an equation developed in subjects with a wide age range by Kyle et al. (FFM(GEN)). Bland-Altman analysis was performed to compare FFM(REF) with FFM(GOT), FFM(WAG), FFM(FHS), and FFM(GEN), respectively. FFM(GOT) also was compared with FFM derived from these published equations. RESULTS: Compared with FFM(REF), the FFM(FHS) and FFM(WAG) underestimated FFM by 2.6 and 7.9 kg in males and 4.2 and 9 kg in females, respectively. The FFM(GEN) underestimated FFM in females by 1.3 kg but not in males (mean difference, -0.04 kg). FFM calculated from the BIA equation developed in this population (FFM(GOT)) neither underestimated nor overestimated FFM as compared with FFM(REF), as expected. The differences between FFM(GOT) and FFMs predicted from these equations were of the same magnitude as that observed with FFM(REF). CONCLUSION: Different prediction equations produced different values for FFM. The age-specific equations developed in other populations underestimated FFM, whereas FFM(GEN) produced an unbiased estimate of FFM in males but not in females. Thus, the BIA prediction equation needs to be developed and validated in the population under study.     

Assessment of bioelectrical impedance analysis for the prediction of total body water in cystic fibrosis

The aim of this study was to compare the measurement of total body water (TBW) by deuterium (2H2O) dilution and bioelectrical impedance analysis (BIA) in patients with cystic fibrosis (CF) and healthy controls. Thirty-six clinically stable patients with CF (age 25.4+/-5.6 yrs) and 42 healthy controls (age 25.4+/-4.8) were recruited into this study. TBW was measured by 2H2O dilution and predicted by BIA in patients and controls. The TBW predicted from BIA was significantly different from TBW as measured using 2H2O in patients (P<0.05) but not in controls. Mean (+/-SD) values for predicted and measured TBW differed by 5.6 (+/-9.1) L in patients and 0.4 (+/-3.6)L in controls. This bias was consistent for all controls but not for patients. In CF, BIA over predicted TBW determined by 2H2O dilution to an increasing extent at larger TBW volumes. There was a strong correlation between height2/impedance and TBW in patients with CF (r=0.90; y=0.67x+2.50) and in controls (r=0.81; y=0.57x+9.60). The slope of the regression lines was similar for both groups, however the y intercepts were significantly different (P<0.05). BIA overestimates TBW in patients with CF, possibly due to invalid factory installed regression equations within BIA instrumentation. Future studies employing BIA as a measure of TBW or FFM in CF should use alternative predictive equations to those that have been developed for healthy individuals. A large scale study to develop specific regression equations for use in CF is warranted.     

Prediction of fat-free mass by bioelectrical impedance analysis in older adults from developing countries: A cross-validation study using the deuterium dilution method

Objective

Several limitations of published bioelectrical impedance analysis (BIA) equations have been reported. The aims were to develop in a multiethnic, elderly population a new prediction equation and cross-validate it along with some published BIA equations for estimating fat-free mass using deuterium oxide dilution as the reference method.

Design and setting

Cross-sectional study of elderly from five developing countries.

Methods

Total body water (TBW) measured by deuterium dilution was used to determine fat-free mass (FFM) in 383 subjects. Anthropometric and BIA variables were also measured. Only 377 subjects were included for the analysis, randomly divided into development and cross-validation groups after stratified by gender. Stepwise model selection was used to generate the model and Bland Altman analysis was used to test agreement.

Results

FFM = 2.95 ? 3.89 (Gender) + 0.514 (Ht2/Z) + 0.090 (Waist) + 0.156 (Body weight). The model fit parameters were an R², total F-Ratio, and the SEE of 0.88, 314.3, and 3.3, respectively. None of the published BIA equations met the criteria for agreement. The new BIA equation underestimated FFM by just 0.3 kg in the cross-validation sample. The mean of the difference between FFM by TBW and the new BIA equation were not significantly different; 95% of the differences were between the limits of agreement of -6.3 to 6.9 kg of FFM. There was no significant association between the mean of the differences and their averages (r= 0.008 and p= 0.2).

Conclusions

This new BIA equation offers a valid option compared with some of the current published BIA equations to estimate FFM in elderly subjects from five developing countries.     

Bioelectrical impedance analysis models for prediction of total body water and fat-free mass in healthy and HIV-infected children and adolescents

BACKGROUND: Bioelectrical impedance analysis (BIA) is an attractive method of measuring pediatric body composition in the field, but the applicability of existing equations to diverse populations has been questioned. OBJECTIVE: The objectives were to evaluate the performance of 13 published pediatric BIA-based predictive equations for total body water (TBW) and fat-free mass (FFM) and to refit the best-performing models. DESIGN: We used TBW by deuterium dilution, FFM by dual-energy X-ray absorptiometry, and BIA-derived variables to evaluate BIA models in a cross-sectional study of 1291 pediatric subjects aged 4-18 y, from several ethnic backgrounds, including 54 children with HIV infection and 627 females. The best-performing models were refitted according to criterion values from this population, cross-validated, and assessed for performance. Additional variables were added to improve the predictive accuracy of the equations. RESULTS: The correlation between predicted and criterion values was high for all models tested, but bias and precision improved with the refitted models. The 95% limits of agreement between predicted and criterion values were 16% and 11% for TBW and FFM, respectively. Bias was significant for some subgroups, and there was greater loss of precision in specific age groups and pubertal stages. The models with additional variables eliminated bias, but the limits of agreement and the loss of precision persisted. CONCLUSION: This study confirms that BIA prediction models may not be appropriate for individual evaluation but are suitable for population studies. Additional variables may be necessary to eliminate bias for specific subgroups.     

Body composition in underweight elderly subjects: reliability of bioelectrical impedance analysis

BACKGROUND AND AIMS: In underweight elderly subjects it is important to estimate body composition and particularly fat-free mass (FFM). Bioelectrical impedance analysis (BIA) is a non-invasive method in determining FFM, but its usefulness in these frail subjects should be verified. The aim of this study is to verify in underweight elderly people the reliability of previously published BIA formulas in detecting FFM. METHODS: Fifty-seven hospitalized elderly subjects (27 males and 30 females) with body mass index <20 kg/m(2) were selected. In all subjects, FFM was detected by dual energy X-ray absorptiometry. Moreover, BIA measurements were performed at standard frequency (50 kHz and 800 microA) and FFM was derived using the main previous published BIA equations. Results: In men, Kyle and Rising equations gave acceptable estimates of FFM with a mean error, respectively, of 1+/-1.9 and 1.4+/-1.7 kg. Also RJL formula could be used after adjusting for a correction factor. In women, no equation seemed sufficiently reliable to estimate FFM. CONCLUSIONS: BIA method seems useful to evaluate body composition in underweight elderly men but it seems to have intrinsic limits in women. Nevertheless, the variability in behavior of the different equations suggests to be careful in adopting BIA equations.     

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

INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

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

Background: 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. Methods: 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. Results: 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. Conclusions: 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.     

Single prediction equation for bioelectrical impedance analysis in adults aged 20--94 years

Existing equations for bioelectrical impedance analysis (BIA) are of limited use when subjects age or become overweight because these equations were developed in young, normal-weight subjects and are not valid in elderly or overweight people. The purpose of this study was to validate a single BIA equation in healthy white subjects aged 22--94 y with a body mass index between 17.0 and 33.8 kg/m(2). Healthy subjects (202 men and 141 women) aged 20--94 y were measured by two methods: fat-free mass (FFM) was measured by dual-energy x-ray absorptiometry (Hologic QDR-4500) and by a bioelectrical impedance analyzer (Xitron 4000B). Validity of BIA was assessed by double cross validation. Because correlations were high (r = 0.986--0.987) and prediction errors low, a single equation was developed using all subjects, as follows: FFM = -4.104 + (0.518 x height(2)/resistance) + (0.231 x weight) + (0.130 x reactance) + (4.229 x sex: men = 1, women = 0). FFM predicted with dual-energy x-ray absorptiometry was 54.0 +/- 10.7 kg. BIA-predicted FFM was 54.0 +/- 10.5 kg (r = 0.986, standard error of the estimate = 1.72 kg, technical error = 1.74 kg). In conclusion, the new Geneva BIA equation was valid for prediction of FFM in healthy adults aged 22--94 y with body mass indexes between 17.0 and 33.8 kg/m(2). Inclusion of reactance in the single prediction equation appeared to be essential for use of BIA equations in populations with large variations in age or body mass.     

Body water compartment measurements: a comparison of bioelectrical impedance analysis with tritium and sodium bromide dilution techniques

BACKGROUND AND AIMS: This study was undertaken to assess the comparability of body water compartment estimates in healthy volunteers using single and dual frequency bioelectrical impedance analysis (BIA) with established reference methods of tritium and NaBr dilution. METHODS: Total body water (TBW) was estimated in 10 healthy volunteers using single frequency (50 kHz) BIA (Bodystat 1500), dual frequency (5 and 200 kHz) BIA (Bodystat Dualscan 2005) and tritium dilution. Extracellular water (ECW) was measured with dual frequency BIA and NaBr dilution. BIA was performed using distal tetrapolar electrodes in the supine position. Venous blood was sampled for measurement of background concentrations of tritium and NaBr using a beta counter and high performance liquid chromatography respectively. 10 ml tritiated water (3.7 MBq) and 50 ml 5% NaBr solution were then injected intravenously and blood samples taken from the opposite arm every 45 min for 4.5 h for estimation of concentrations of tritium and NaBr. RESULTS: There was good correlation (r(2)=0.76) between estimates of ECW using dual frequency BIA and NaBr dilution, with the former overestimating ECW by approximately 1 L. However, this difference varied systematically with body weight. Although TBW measurements obtained by single and dual frequency BIA correlated well with estimates using tritium dilution (r(2)=0.96 and 0.95 respectively), single frequency BIA underestimated TBW by approximately 1 L and dual frequency BIA by approximately 5 L compared to tritium dilution. CONCLUSION: TBW measurements obtained using the single frequency BIA device were more accurate than those obtained using the dual frequency BIA device. Dual frequency BIA provided a reasonably accurate estimate of ECW.     

A longitudinal comparison of body composition by total body water and bioelectrical impedance in adolescent girls

Previous studies have assessed the ability of bioelectrical impedance analysis (BIA) to estimate body composition cross-sectionally, but less is known about the ability of BIA to detect changes in body composition longitudinally over the adolescent growth period. Body composition was assessed by isotopic dilution of H(2)(18)O and BIA in 196 initially nonobese girls enrolled in a longitudinal study. Two prediction equations for use in our population of girls were developed, one for use premenarcheally and one for use postmenarcheally. We compared estimates from our equation with those derived from several published equations. Using longitudinal data analysis techniques, we estimated changes in fat-free mass (FFM) and percentage body fat (%BF) over time from BIA, compared with changes in FFM and % BF estimated by H(2)(18)O. A total of 422 measurements from 196 girls were available for analysis. Of the participants, 26% had one measurement of body composition, 43% had two measurements of body composition and 31% had three or more measurements of body composition. By either H(2)(18)O or BIA, the mean %BF at study entry was 23% (n = 196) and the mean %BF at 4 y postmenarche was 27% (n = 133). In our cohort, the best predictive equations to estimate FFM by BIA were: PREMENARCHE: FFM = -5.508 + (0.420 x height(2)/resistance) + (0.209 x weight) + (0.08593 x height) + (0.515 x black race) - (0.02273 x other race). POSTMENARCHE: FFM = -11.937 + (0.389 x height(2)/resistance) + (0.285 x weight) + (0.124 x height) + (0.543 x black race) + (0.393 x other race). Overall, we found that BIA provided accurate estimates of the change in both FFM and %BF over time.     

Evaluation of a new bioelectrical impedance instrument for the prediction of body cell mass independently of height or weight

The objective of the present study was to evaluate the performance of a new bioelectrical impedance instrument, the Soft Tissue Analyzer (STA), which predicts a subject's body composition. A cross-sectional population study in which the impedance of 205 healthy adult subjects was measured using the STA. Extracellular water (ECW) volume (as a percentage of total body water, TBW) and fat-free mass (FFM) were predicted by both the STA and a compartmental model, and compared according to correlation and limits of agreement analysis, with the equivalent data obtained by independent reference methods of measurement (TBW measured by D(2)O dilution, and FFM measured by dual-energy X-ray absorptiometry). There was a small (2.0 kg) but significant (P < 0.02) difference in mean FFM predicted by the STA, compared with the reference technique in the males, but not in the females (-0.4 kg) or in the combined group (0.8 kg). Both methods were highly correlated. Similarly, small but significant differences for predicted mean ECW volume were observed. The limits of agreement for FFM and ECW were -7.5-9.9 and -4.1-3.0 kg, respectively. Both FFM and ECW (as a percentage of TBW) are well predicted by the STA on a population basis, but the magnitude of the limits of agreement with reference methods may preclude its usefulness for predicting body composition in an individual. In addition, the theoretical basis of an impedance method that does not include a measure of conductor length requires further validation.     

Application of bioelectric impedance methodology and prediction equations to determine the volume of distribution for ethanol

In large-scale epidemiologic studies of drinking behavior there is a need for simple and reliable estimates of the body water compartment of subjects. This, in turn, provides an estimate of the volume of distribution of ingested ethanol and a better estimate of tissue exposure levels than the use of total body weight as the volume of distribution for alcohol. The volume of distribution for ethanol (total body water, TBW) was estimated in a racially mixed group of 276 alcoholics and 166 nonalcoholics (aged 20–59 years) by means of bioelectric impedance methodology (BIA) and by means of prediction equations based upon age, body weight, and height. Estimations of mean TBW from BIA were found to be only slightly higher (1–40%) than those provided by the prediction equations. TBW values generated from both prediction equations were also highly correlated with TBW values obtained by impedance methodology, with the highest correlations observed in females (particularly black) and in alcoholics (particularly female).     

Impact of indexing resting metabolic rate against fat-free mass determined by different body composition models

OBJECTIVE: To examine the differences arising from indexing resting metabolic rate (RMR) against fat-free mass (FFM) determined using two-, three- and four-compartment body composition models. DESIGN: All RMR and body composition measurements were conducted on the same day for each subject following compliance with premeasurement protocols. SUBJECTS: Data were generated from measurements on 104 males (age 32.1+/-12.1 y (mean+/-s.d.); body mass 81.15+/-12.85 kg; height 179.5+/-6.5 cm; body fat 20.6+/-7.6%). INTERVENTIONS: Body density (BD), total body water (TBW) and bone mineral mass (BMM) were measured by hydrodensitometry, deuterium dilution and dual energy X-ray absorptiometry (DXA), respectively. These measures were used to determine two (hydrodensitometry: BD; hydrometry: TBW)-, three (BD and TBW)- and four- compartment (BD, TBW and BMM) FFM values. DXA also provided three compartment derived FFM values. RMR was measured using open circuit indirect calorimetry. RESULTS: Three (body fat group: lean, moderate, high) x five (body composition determination: hydrodensitometry, hydrometry, three-compartment, DXA, four-compartment) ANOVAs were conducted on FFM and RMR kJ.kg FFM(-1).d(-1). Within-group comparisons revealed that hydrodensitometry and DXA were associated with significant (P<0.001) overestimations and underestimations of FFM and RMR kJ.kg FFM(-1).d(-1), respectively, compared with four-compartment-derived criterion values. A significant interaction (P<0.001) resulted from DXA's greater deviations from criterion values in lean subjects. While hydrometric means were not significantly (P> or =0.68) different from criterion values intraindividual differences were large (FFM: -1.5 to 2.9 kg; RMR: -6.0 to 3.2 kJ.kg FFM(-1).d(-1)). CONCLUSION: The relationship between RMR kJ.kg FFM(-1).d(-1) and exercise status would best be investigated using three (BD, TBW)- or four (BD, TBW, BMM)-compartment body composition models to determine FFM. Other models either significantly underestimate indexed RMR (hydrodensitometry, DXA) or display large intraindividual differences (hydrometry) compared with four-compartment derived criterion values. SPONSORSHIP: Australian Research Council (small grants scheme).     

Multiple frequency bioimpedance: a bed-side technique for assessment of fluid shift patterns in a patient with severe dehydration

This report describes the use of multiple frequency bioimpedance analysis (MFBIA) to monitor fluid changes in a patient who developed severe dehydration and recovered. Initially, the patient weighed 53.2 kg, his total body water (TBW; D(2)0 dilution) was 33.5 L, his extracellular water (ECW; Br dilution) was 19.5 L, and hydration of the fat-free mass (FFM; dual-energy X-ray absorptiometry) was normal (73%). The resistances at infinite and 0 frequency were R(inf) = 454 and R(0) = 580 ohm respectively, which predicted TBW = 33.1 L and ECW = 16.6 L. On day 7, when the weight loss was 7.2 kg, FFM had decreased by 7.4 kg, and R(inf) and R(0) had increased to 662 and 902 ohm respectively, predicting decreases of 5.8 L in TBW and 3.7 L in ECW. On recovery (day 14), all parameters had returned to baseline values. This study encourages the use of MFBIA as a bed-side technique for the serial assessment of body water compartments in patients with disturbances in fluid balance.     

Validation of body composition determination by bioelectrical impedance analysis in acromegaly.

Body composition determination by bioelectrical impedance analysis (BIA) has been compared with measurement of total body water (TBW) by tritiated water dilution and estimation of body fat (BF) by measurement of TBW and total body potassium (TBK) in a four-compartment model, in patients with acromegaly. This disorder is accompanied by a profound aberration in body composition. Furthermore TBW and BF were predicted on the basis of anthropometric variables alone. Paired comparisons of TBW estimations by isotope dilution and BIA showed good correlation (Spearman's rank correlation 0.95, P less than 0.01). Isotope dilution resulted in a mean of 1.7 liter (standard deviation 1.87) higher values. Comparison of BF estimations showed also a significant correlation (Spearman's rank correlation 0.75, P less than 0.01), with slightly higher values for BIA (mean 1.4 kg; standard deviation 2.99). BIA improved the prediction of TBW and BF compared with predictions based on anthropometric variables. In a population of acromegalic patients, BIA seemed to be a useful method to estimate TBW and BF.     

Evaluation of equations for fat-free mass based on anthropometry in infants and young children in South Asia

Rapid postnatal growth in low-birth weight infants increases the risk of hypertension, CHD and type 2 diabetes in adult life. To provide validated tools to study the growth in South Asian infants, we evaluated two published equations to measure total body water (TBW) and fat-free mass (FFM) based on anthropometry in 6- to 24-month-old infants, using 2H2O dilution. In a method-comparison study in seventy-eight infants aged 6-24 months (forty-two girls and thirty-six boys) from the urban poor attending an immunisation clinic of a hospital in Kolkata, we measured their length to the nearest 0.1 cm, weight to the nearest 10 g and TBW using 2H2O dilution. The calculated TBW in kg (TBWkg) and FFM in kg (FFMkg) using two equations based on the length and weight were each compared with TBWkg and FFMkg calculated from 2H2O dilution. The mean FFMkg were 7.31 (sd 1.11), 7.13 (SD 1.08) and 7.26 (SD 1.13) by the 2H2O dilution method, and the anthropometry equations of Mellits and Cheek (AN-1) and Morgenstern et al. (AN-2), respectively. The mean of the paired difference in FFMkg was 0.18 (SEM 0.06) and 0.04 (SEM 0.07) between 2H2O, and AN-1 and AN-2, respectively. There is a good agreement for FFM derived by AN-2 with 2H2O dilution. The former is 1% lower than that obtained from the reference method (P=0.28). The AN-2 equation is useful for evaluating FFM in infants in India.     

Body composition in the elderly: Total body water and anthropometry

Body composition measured with isotopic dilution was compared with anthropometric measurements. The study was carried out in 47 subjects from both sexes, 65 to 92 years old. Total body water (TBW), anthropometric measurements, and dynamometry were assessed. TBW was significatively higher in men than women and decreased with age. Dynamometry and fatfree mass were well correlated (r=0.73 in males and r=0.58 in females) and significantly different between sexes. A negative correlation was found for dynamometry with age, being significant for women. Linear regression equations to predict TBW from anthropometric measurements in males and females were obtained: Males: TBW(I)=19.349+0.617 weight(kg) — 0.931 mid-arm circumference(cm)+0.122 dynamometry (kg) Females: TBW(l)=−5.531+0.343 weight(kg)-0.213 triceps skinfold (mm)+ 0.148 dynamometry(kg) + 3.424 wrist diameter (cm). This simple model is proposed for use in epidemiological and field studies where other more sophisticated methods can not be applied.     

Estimation of total body water by bioelectrical impedance analysis

Total body water (TBW) measured by bioelectrical impedance analysis (BIA) was directly compared with deuterium-isotope dilution in a total of 58 subjects. First, sex-specific and group equations were developed by multiple regression analysis in (10 each) obese and nonobese men and women. Height/resistive impedance was the most significant variable used to predict deuterium-dilution space (D2O-TBW) and, combined with weight, yielded R = 0.99 and SE of estimate = 1.75 L. Equations predicted D2O-TBW equally well for obese and nonobese subjects. Second, the equations were prospectively tested in a heterogeneous group of 6 males and 12 females. Sex-specific equations predicted D2O-TBW with good correlation coefficients (0.96 and 0.93), total error (2.34 and 2.89 L), and a small difference between mean predicted and measured D2O-TBW (-1.4 +/- 2.05 and -0.48 +/- 2.83 L). BIA predicts D2O-TBW more accurately than weight, height, and/or age. A larger population is required to validate the applicability of our equations.