Determination of total body water by deuterium NMR

Fat deposition and partitioning for meat production in cattle and sheep

In markets for beef and sheep meat, an appropriate level of intramuscular fat (IMF) is highly desirable for meat-eating quality, but strategies to improve it usually lead to an undesirable excess in carcase fat, presenting a major challenge to livestock producers. To solve this problem, we need to understand the partitioning of fat among the major fat depots: IMF, subcutaneous fat (SCF) and visceral fat (VF). In most genotypes of cattle and sheep, the rate of accretion is lower for IMF than for SCF and VF, so genetic selection for a high level of IMF, or the use of an increased dietary energy supply to promote IMF deposition, will increase overall fatness and feed costs. On the other hand, feeding postnatal calves with excessive concentrates promotes IMF deposition, so a nutritional strategy is feasible. With genetic strategies, several problems arise: 1) positive genetic correlations between IMF, SCF and VF differ among genotypes in both cattle and sheep; 2) genotypes appear to have specific, characteristic rates of accretion of IMF during periods of growth and fattening; 3) most breeds of cattle and sheep naturally produce meat with relatively low levels of IMF, but IMF does vary substantially among individuals and breeds so progress is possible through accurate measurement of IMF. Therefore, an essential prerequisite for selection will be knowledge of the genetic correlations and fat accretion rates for each genotype. Currently, selection for IMF is based on existing technology that directly measures IMF in the progeny or siblings, or estimates IMF in live animals. New technology is needed to permit the simultaneous measurement of SCF and IMF in the field, thus opening up the possibility of accurate selection, particularly for fat partitioning in live animals. Specifically, there would be great value in detecting individuals with an IMF advantage at an early age so the generation interval could be shortened and genetic gain accelerated. Genetic gain would also be greatly aided if we could select for genes that control adipogenesis and lipogenesis and are also differentially expressed in the various depots.

Determination of Isotope Abundance for Deuterium-labeled Compounds by Quantitative 1 H NMR + 2 H NMR

Deuterated reagents have been used in many research fields. Isotope abundance, as the feature parameter of deuterated reagents, the precise quantification is of great importance. Based on quantitative nuclear magnetic resonance technology, a novel method that combines ¹ H NMR + ² H NMR was systematically established to determine the isotopic abundance of deuterated reagents. The results showed that the isotopic abundance of partially labeled and fully labeled compounds calculated by this new method was even more accurate than that calculated by classical ¹ H NMR and MS methods. In brief, this new method is a robust strategy for the determination of isotope abundance in large-scale deuterated reagents.

Impact of empagliflozin on subclinical left ventricular dysfunctions and on the mechanisms involved in myocardial disease progression in type 2 diabetes: rationale and design of the EMPA-HEART trial

Background

Asymptomatic left ventricular (LV) dysfunction is highly prevalent in type 2 diabetes patients. Unlike the other hypoglycemic drugs, SGLT2 inhibitors have shown potential benefits for reducing cardiovascular death and risk factors, aside from lowering plasma glucose levels. With this study we aim at determining whether the treatment with empagliflozin is associated with an improvement in LV functions in diabetic patients with asymptomatic LV dysfunction against Sitagliptin, which is presumably neutral on myocardial function. To determine changes in LV systolic and diastolic functions we will use speckle-tracking echocardiography, a novel sensitive, non-invasive, bedside method allowing the calculation of LV global longitudinal strain (GLS), an index of myocardial deformability, as well as 3D echocardiography, which allows a better evaluation of LV volumes and mass.

Methods

The EMPA-HEART trial will be a phase III, open label, active-controlled, parallel groups, single centre, exploratory study conducted in Pisa, Italy. A cohort of 75 diabetic patients with normal LV systolic (2D-Echo EF > 50%) and renal (eGFR sec MDRD > 60 ml/min/1.73 mq) functions and no evidence of valvular and/or ischemic heart disease will be randomized to either Empagliflozin 10 mg/die or Sitagliptin 100 mg/die. The primary outcome is to detect a change in GLS from baseline to 1 and 6 months after treatment initiation. The secondary outcomes include changes from baseline to 6 months in 3-D Echocardiography EF, left atrial volume and E/E′, VO₂max as measured at cardiopulmonary test, cardiac autonomic function tests (R–R interval during Valsalva manoeuvre, deep-breathing, lying-to-standing), and the determination of a set of plasma biomarkers aimed at studying volume, inflammation, oxidative stress, matrix remodelling, myocyte strain and injury.

Discussion

SGLT2 inhibitors might affect myocardial functions through mechanisms acting both directly and indirectly on the myocardium. The set of instrumental and biohumoral tests of our study might actually detect the presence and entity of empagliflozin beneficial effects on the myocardium and shed light on the mechanisms involved. Further, this study might eventually provide information to design a clinical strategy, based on echocardiography and/or biomarkers, to select the patients who might benefit more from this intervention.

Trial registration EUDRACT Code 2016-0022250-10

Changes in total body water content during running races of 21.1 km and 56 km in athletes drinking ad libitum

OBJECTIVE

To measure changes in body mass (BM), total body water (TBW), fluid intake, and blood biochemistry in athletes during 21.1-km and 56-km foot races.

DESIGN

Observational study.

SETTING

2009 Two Oceans Marathon, South Africa.

PARTICIPANTS

Twenty-one (21.1 km) and 12 (56 km) participants were advised to drink according to thirst or their own race drink plan (ad libitum).

MAIN OUTCOME MEASURES

Body mass, TBW, plasma osmolality, plasma sodium (p[Na]), and plasma total protein ([TP]) concentrations were measured before and after race. Fluid intake was recorded from recall after race.

RESULTS

Significant BM loss occurred in both races (21.1 km; -1.4 ± 0.6 kg; P < 0.000 and 56 km; -2.5 ± 1.1 kg; P < 0.000). Total body water was reduced in the 56-km race (-1.4 ± 1.1 kg; P < 0.001). A negative linear relationship was found between percentage change (%Δ) in TBW and %Δ in BM in the 56-km runners (r = 0.6; P < 0.01). Plasma osmolality and [TP] increased significantly in the 56-km runners (6.8 ± 8.2 mOsm/kg H2O; P < 0.05 and 5.4 ± 4.4 g/L; P < 0.01, respectively), but all other biochemical measures were within the normal range.

CONCLUSIONS

Although TBW decreased in the 56-km race and was maintained in the 21.1-km race, the change in TBW over both races was less than the BM, suggesting that not all BM lost during endurance exercise is a result purely of an equivalent reduction in TBW. These findings support the interpretation that the body primarily defends p[Na] and not BM during exercise and that a reduction in BM can occur without an equivalent reduction in TBW during prolonged exercise. Furthermore, these data support that drinking without controlling for BM loss may allow athletes to complete these events.

Validity of two-component models for estimating body fat of black men

Commonly used two-component model conversion formulas that estimate relative body fat (%BF) from body density (Db) were cross-validated on a heterogeneous sample of black men (n = 30; age = 19--45 yr). A four-component model was used to obtain criterion measures of %BF, and linear regression and analysis of individual residual scores were conducted to assess the predictive accuracy of the formulas under investigation. The two-component formula commonly used to estimate %BF of black men (Schutte JE, Townsend EJ, Hugg J, Shoup RF, Malina RM, and Blomqvist CG. J Appl Physiol 56: 1647-1649, 1984) significantly (P < or = 0.01) and systematically (87% of sample) overestimated %BF (-1.28%); thus we developed the following two-component Db conversion formula: %BF = [(4.858/Db) - 4.394] x 100. Because our formula was derived from a four-component model and a larger, more heterogeneous sample than the commonly used two-component formula, we recommend using it to convert Db to %BF for black men. Additionally, there was good agreement between dual-energy X-ray absorptiometry and the four-component model, making this a suitable alternative for estimating the %BF of black men.

Indirect estimates of body composition are useful for groups but unreliable in individuals

OBJECTIVE

To assess the usefulness of the body mass index (BMI) in identifying individuals classified as overweight or obese based on estimates of body fat percentage (BF%) obtained by the deuterium dilution (BF%DD) method. In addition, to assess the accuracy of bioelectrical impedance analysis (BIA) and skinfold thickness (SFT) measurements in the estimation of body composition of Australians at the individual and group level.

DESIGN

Cross-sectional study.

SUBJECTS

One hundred and seventeen healthy Australian volunteers of European descent, comprising of 51 males and 66 females, ranging in age from 19 to 77 y.

MEASUREMENTS

BMI was calculated from body weight and height. Fat-free mass (FFM) was estimated from measures of total body water (TBW) using deuterium dilution (FFM(DD)), SFT using the equations of Durnin and Womersley (Br J Nutr 1974; 32: 77-97) (FFM(SFT)), and BIA using the equations of Lukaski et al (J Appl Physiol 1986; 60: 1327-1332) (FFM(Lu)), Segal et al (Am J Clin Nutr 1988; 47: 7-14) (FFM(Se)) and Heitmann (Eur J Clin Nutr 1990; 44: 831-837) (FFM(He)). Estimates of fat mass (FM) were calculated as the difference between body weight and FFM, while BF% was calculated by expressing FM as a percentage of body weight.

RESULTS

BMI had poor sensitivity and positive predictive value in identifying individuals as being overweight/obese as classified by BF%DD. Furthermore, estimates of FFM (and hence FM) from BIA or SFT could not be used interchangeably with DD, without the risk of considerable error at the individual level. At the group level errors were relatively smaller, though statistically significant. While FFM(SFT) could be corrected by the addition of the bias (1.2 kg in males and 0.8 kg in females), no simple correction was possible with BIA estimates of FFM for any of the equations used. However, an accurate prediction of FFM(DD) was possible from the combination of FFM(He), biceps SFT and mid-arm circumference in both males and females. The bias of this prediction was small (<0.15 kg), statistically non-significant in both sexes, and unrelated to the mean FFM obtained by the two methods. The revision of Heitmann's estimate of FFM using anthropometric variables described in this study had the best sensitivity (79%), specificity (96%) and positive predictive value (92%) in identifying overweight/obese individuals in comparison to the other equations tested.

CONCLUSION

BMI was a poor surrogate for body fatness in both males and females. The currently recommended equations for the prediction of body composition from SFT and BIA provided inaccurate estimates of FFM both at the individual and group level as compared to estimates from DD. However, Heitmann's equations, when combined with measures of the biceps SFT and mid-arm circumference, provided better estimates of FFM both at the individual and group level.

Techniques of body composition assessment: a review of laboratory and field methods

Body composition is one of the major health-related components of fitness. Thus, it is important for health and fitness professionals to have a general understanding of the most commonly used techniques for assessing body composition. This review presents the developmental background and underlying principles and theory of four laboratory (hydrodensitometry, air displacement plethysmography, isotope dilution, and dual-energy x-ray absorptiometry) and four field (bioelectrical impedance analysis, near-infrared interactance, skinfolds, and anthropometry) methods of body composition assessment. In addition to a description of the methods, the validity, and reliability, strengths, and limitations of each measurement tool are examined. Highlights of the laboratory methods include the relatively new Bod Pod air displacement device, which is a promising assessment tool more convenient than hydrodensitometry but still lacking substantial validity testing and the ability of dual-energy x-ray absorptiometry to measure regional composition making it an attractive method for clinicians. Advancements in segmental and multifrequency bioelectrical impedance for compartmental analysis have enhanced the value of this field method, but research continues to show that commercially available near-infrared interactance units are invalid. With this knowledge, the clinician and researcher should be able to make an informed decision regarding the most appropriate measurement device for their body composition assessments.

Is there evidence for an age-related reduction in metabolic rate?

To determine whether the age-related reduction in basal metabolic rate (BMR) is explained by a quantitative and/or qualitative change in the components of lean tissue, we conducted a cross-sectional study in groups of young (n = 38, 18-35 yr) and older (n = 24, 50-77 yr) healthy individuals. BMR was measured by indirect calorimetry. Body composition was obtained by using dual-energy X-ray absorptiometry (DEXA), which permitted four compartments to be quantified [bone mineral mass, fat mass (FM), appendicular lean tissue mass (ALTM), and nonappendicular lean tissue mass (NALTM)]. Absolute BMR and ALTM were lower, whereas FM was significantly higher in the older, compared with young, subjects. BMR, adjusted for differences in FM, ALTM, and NALTM, was significantly lower in the older subjects by 644 kJ/day. In separate regression analyses of BMR on body compartments, older subjects had significantly lower regression coefficients for ALTM and NALTM, compared with young subjects. Hence, the age-related decline in BMR is partly explained by a reduction in the quantity, as well as the metabolic activity, of DEXA-derived lean tissue components.

Fourier transform infrared spectroscopy measures 1H/2H ratios of native water with a precision comparable to that of isotope ratio mass spectrometry

A fast and easy method is described which uses Fourier transform infrared spectroscopy (FT-IR) to measure the 1H/2H ratio of aqueous samples of less than 100 microliters with high precision (+/- 0.2-0.5% in the range of 89 to 2680 microliters/l). Using a thermostat-controlled CaF2 cell, low resolution absorption specta (8 cm-1) are measured. The integral of absorption in the range of 2600 and 2460 cm-1 (O2H vibration) is used to analyse the 2H content of the sample. For measurements at low enrichment five standards are used (SLAP: 89.00 microliters/l, GISP: 126.3 microliters/l, V-SMOW: 156.0 microliters/l, all from the International Atomic Energy Agency, Vienna, Austria, standard 1: 183.3 microliters/l, standard 2: 222.5 microliters/l, both prepared by weighing and controlled by isotope ratio mass spectrometry (IR-MS)). For measurements at high enrichment three standards are used (standard 2: 222.5 microliters/l, standard 3: 1323 microliters/l, standard 4: 2680 microliters/l, all prepared by weighing and controlled by IR-MS). Measured and reported 2H concentrations coincide very well, two samples for quality control (145 and 1612 microliters/l) were measured with a precision of 0.3 and 0.4% corresponding to +/- 0.5 and 5.9 microliters/l.

Measurement of nutrient intake by deuterium dilution in premature infants

To assess whether a simple nonrestrictive method of determining nutrient intake could be applied to premature infants, we compared actual measured formula intake during a 7-day period with intake calculated from deuterium dilution in 13 hospitalized, growing, premature newborn infants. An oral dose of deuterium oxide (D2O) was administered, and urine samples were analyzed by deuterium nuclear magnetic resonance spectrometry for D2O concentration. Using an exponential model, we calculated formula intake from the decline in D2O concentration during the 7-day study period. Intake as assessed by the deuterium model correlated well with actual intake (r = 0.93; p < 0.001). However, because the deuterium dilution model measures both dietary and nondietary water intake (metabolic and cutaneous water influx), deuterium dilution-derived intake exceeded actual intake by 25 +/- 18 ml/kg per day (16% +/- 11%). When corrections were applied to account for nondietary water intake, deuterium dilution-derived nutrient intake (160 +/- 30 ml/kg per day) closely approximated actual intake (155 +/- 17 ml/kg per day). If corrections are made for nondietary water intake, the deuterium dilution method may be a useful nonrestrictive method of measuring nutrient intake in a variety of neonatal populations.

Impaired recovery of strength in older patients after major abdominal surgery

OBJECTIVE

This study compared changes in muscle strength after major elective abdominal surgery in young and old patients, and related these changes to body composition and nitrogen balance.

SUMMARY BACKGROUND DATA

The breakdown of muscle protein, erosion of lean tissue, and negative nitrogen balance are characteristic metabolic responses to surgical illness. With a substantial loss of muscle mass typical of advancing age, the authors postulated that older patients would be weaker during acute surgical illness and less able to maintain muscle function and meet metabolic demands.

METHODS

Active, community-dwelling individuals undergoing major abdominal procedures who were 70 years of age or older or 50 years of age or younger were studied. Total body water (TBW) was determined preoperatively by deuterium oxide dilution. Maximal voluntary handgrip, respiratory muscle strength, and visual analog pain scores were measured preoperatively and on postoperative days 2, 4, and 6. All urine was collected postoperatively for 7 days for determination of total nitrogen, creatinine, and cortisol.

RESULTS

The young (age, 36 +/- 9 years [mean +/- standard deviation]; n = 20) and old groups (age, 77 +/- 5 years; n = 20) were similar regarding weight, sex distribution, nutritional status, surgical procedures and anesthesia, and postoperative urine cortisol values. Age group, time after operation, and interaction effects were significant for each strength variable (all p < 0.005 by analysis of variance). Older patients had lower preoperative strength (29% to 41%) and mean 24-hour urine creatinine (27%). Postoperative strength was decreased most markedly on postoperative day 2, with similar proportional changes in the two age groups but lower absolute levels in the older patients. The rate of recovery of strength was substantially less rapid and complete in older patients. Older patients had less postoperative pain and received much less parenteral narcotic than younger patients. Postoperative urine nitrogen was similar in each group. Recovery of strength was not related to malignancy, preoperative strength, muscle mass (urine creatinine), lean body mass (TBW), sex, malignancy, pain, or narcotic administration.

CONCLUSIONS

Older patients are weaker preoperatively than younger patients; their strength falls to lower levels after surgery and their postoperative recovery of strength is impaired. The lesser preoperative strength of older patients is due in large part but not totally to diminished muscle mass. Their impaired postoperative recovery appears to be related to more acute factors, such as muscle energetics or substrate availability.

Effect of intrauterine growth retardation on postnatal weight change in preterm infants

To investigate the cause or causes of early postnatal weight change, we measured total body water and fluid and energy balances in 14 preterm infants who were appropriate in size for gestational age (AGA) and in 5 weight-matched, preterm, small-for-gestational-age (SGA) infants. On the first day of life, AGA and SGA infants had the same weight and total body water content. At 6 +/- 2 days (mean +/- SD), AGA infants had had significant weight loss (94 +/- 45 gm) and body water loss (67 +/- 80 ml), whereas weight and total body water content in the SGA infants at the same age (5 +/- 1 days) did not differ from the values at birth. Loss of weight and total body water in AGA infants was accompanied by a greater diuresis than in SGA infants at the same amount of fluid intake. At the end of week 1, AGA and SGA infants had the same total energy expenditure (184 +/- 33 vs 171 +/- 17 kJ.kg-1 x day-1); energy intake, which had exceeded total energy expenditure from the third day of life and beyond, already provided 188 +/- 46 (AGA) or 209 +/- 109 kJ.kg-1 x day-1 (SGA), respectively, for energy storage. Nitrogen balance was positive. Subsequent weight gain occurred at the same rate in AGA and SGA infants; both total body water and solids increased. Energy intake, total energy expenditure, and the amount of energy stored (measured during stable weight gain on a regimen of full enteral feedings) had significantly increased compared with week 1, but both groups maintained similar energy storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein turnover in advanced lung cancer patients

Understanding the extent to which changes in whole-body protein kinetics contribute to the commonly observed weight loss and decrease in lean body mass (LBM) in patients with cancer is currently obscured by conflicting reports in the literature. While several studies have reported significant increases in whole-body protein turnover (WBPT), synthesis (WBPS), and catabolism (WBPC) in patients with cancer, others have failed to confirm these observations. We have measured whole-body protein kinetics using a primed constant infusion of 15N-glycine in a homogenous group of 32 newly diagnosed advanced lung cancer patients with comparable staging and before any antineoplastic treatment, and in 19 normal healthy volunteer controls. Urinary urea and ammonia 15N enrichment was determined in individually collected urine samples obtained during the 24-hour study period and averaged for the determination of protein kinetics. During the last 6 hours of urine collection, samples were obtained hourly for determination of 15N plateau enrichment. Twenty-four-hour urinary nitrogen and creatinine excretion was determined from 24-hour pooled urine samples. Resting metabolic expenditure (RME) was determined by indirect calorimetry and LBM was estimated from deuterium oxide dilution. Age body weight, LBM, RME, and 24-hour urinary nitrogen excretion did not differ between cancer and control subjects. WBPT, WBPC, and WBPS (g/kg/d) were significantly increased in lung cancer patients. However, when the same results were expressed either per kilogram LBM or per gram 24-hour urinary creatinine excretion, WBPT, WBPC, and WBPS rates were not statistically different from those of the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of fat-free mass in black and white pre-adolescent and adolescent girls from anthropometry and impedance

As an ancillary project of the National Heart Lung and Blood Institute's Growth and Health Study (NGHS), data of 31 black girls and 38 white girls, 10-16 years of age, were used to develop equations to predict fat-free mass (FFM) from selected anthropometric dimensions and bioelectric impedance measures of resistance and reactance. Subjects were drawn from ongoing projects at the Children's Hospital Medical Center (CHMC) to obtain girls of both races from a wide range of body mass indices. FFM was estimated from measures of dual energy X-ray absorptiometry (DXA). The resulting equations had a root mean square error (RMSE) of 1.9 kg and a coefficient of variation (CV) of 4.9% for black girls using independent variables: stature divided by resistance squared (S² /R), thigh circumference, subscapular and suprailiac skinfold thicknesses. The corresponding values for white girls were 1.1 kg and 3.2% using independent variables: S² /R, arm circumference, weight, and reactance divided by resistance (R/R_c ). In addition to cross-validating the ethnic-specific equations using PRESS statistics, the equation for white girls was also cross-validated using an independent sample of 35 girls from the Fels Longitudinal Study selected to match the CHMC sample. The cross-validation yielded a pure error of 2.4 kg FFM and a CV of 7%. The predicted values for FFM from the equations were used to calculate percentage of body fat in the CHMC sample and the pure errors for estimating percentage of body fat were 3% for blacks and 2% for whites. © 1993 Wiley-Liss, Inc.

Alterations in body fluid content can be detected by bioelectrical impedance analysis

The electrical resistance across the whole body and its segments to the conduction of a weak alternating current was determined in human subjects under three different conditions: (1) during bed rest, (2) during infusion of 1 liter of saline, and (3) during donation of 1 unit of blood. During bed rest, extracellular and total body water were measured by dilution of bromide and heavy water, respectively. Electrical resistance obtained from electrodes placed on proximal portions of extremities ("proximal resistance") accounted for less than 50% of that determined by electrodes positioned on routinely used portions of a hand and foot ("whole body resistance"). Following saline infusion, resistance determined from the whole body and all its segments fell (P less than 0.001); the magnitude of the drop in both proximal and whole body resistance was inversely related to the volume of total body water (TBW) (r = -0.82, P less than 0.002, and r = -0.73, P less than 0.01, respectively). In contrast, blood donation was associated with significantly increased resistance at both measurement sites. TBW predicted from anthropometrics was inversely related to both proximal (r = -0.90, P less than 0.001) and whole body resistance (r = -0.75, P less than 0.001). Bioelectrical impedance analysis is a simple technique which may be useful in monitoring minimal alterations in TBW. Furthermore, altered fluid status may be predicted more accurately by changes in proximal resistance compared to changes in traditionally used whole body resistance.

Optimum doses of deuterium oxide and sodium bromide for the determination of total body water and extracellular fluid

A practical approach for determining optimum tracer doses is described for measurements of total body water (TBW) and extracellular water (ECW) based on dilution of deuterium oxide and sodium bromide with respective analyses by nuclear magnetic resonance and anion-exchange chromatography. Using these techniques and plasma concentrations corresponding to adult doses up to 1.5 g kg-1 body weight of deuterium oxide and 0.05 g kg-1 of sodium bromide, the variations of analyses of these tracers, at these respective doses, were calculated. TBW determination with an RSD of less than 2% was found to require administration of 0.4 g kg-1 of deuterium oxide. Because basal concentrations of bromide are quantifiable, the accuracy of the extracellular water determination depends upon the magnitude of the increase in plasma bromide concentration; a sodium bromide dose of 0.01 g kg-1 provides a deviation in the determined ECW volume of approximately 1%.

Body composition in Chinese subjects: comparison with data from North America

A multiple tracer dilution method measuring total body water, extracellular water, plasma volume, and red cell volume was used to study body composition. Healthy Chinese subjects were compared to a group of Chinese patients with various newly diagnosed gastrointestinal disorders scheduled for elective operation. Compositional data obtained from these groups showed no significant differences in compartmentalization, suggesting absence of major changes during the early stages of certain gastrointestinal diseases. In addition, healthy Chinese subjects were compared to a group of healthy Americans previously evaluated by similar dilutional methods. In males, body weight (kg) differed considerably (Chinese = 62.1 +/- 2.0 versus American = 72.5 +/- 4.1, p less than 0.02) and could be explained by alterations in body fat (Chinese = 12.4 +/- 1.3 versus American = 19.2 +/- 2.2, p less than 0.02) and extracellular water (Chinese = 14.4 +/- 0.5 versus American = 16.8 +/- 0.8, p less than 0.02). Functional tissue ("body cell mass") was similar in the 2 groups which suggested that Chinese have comparable body composition without an additional fat burden. The multiple tracer technique using deuterium oxide, sodium bromide, Evans dye, and Cr51 for body compositional assessment is accurate but expensive and laborious. Therefore, equally precise but more economical bedside methods are needed for routine compositional analysis.