Body composition analysis by bioelectrical impedance in chronic maintenance dialysis patients: comparisons to the National Health and Nutrition Examination Survey III

Phase Angle as Surrogate Marker of Muscle Weakness in Kidney Transplant Candidates Referred to Prehabilitation

Phase angle (PhA), a marker of nutritional status obtained by bioelectrical impedance analysis (BIA), is associated with the integrity of cell membranes. Damage to muscle fiber membranes can impact muscle strength, which is related to adverse outcomes in adults with advanced chronic kidney disease (CKD). The main objective of this study was to determine the usefulness of the PhA in identifying muscle weakness in candidates for kidney transplants (KTs). Secondly, it aimed to examine the associations of PhA with other parameters of body composition, exercise performance, and muscle structure. Sensitivity, specificity, and area under the receiver operating characteristics curve were used to evaluate the PhA (index test) as a biomarker of muscle weakness. Muscle strength was estimated with maximal voluntary isometric contraction of the quadriceps (MVCI-Q) of the dominant side. Muscle weakness was defined as MVIC-Q < 40% of body weight. A total of 119 patients were evaluated (mean age 63.7 years, 75.6% men). A phase angle cut-off of 5.1° was identified to classify men with a higher likelihood of having low muscle strength in upper limbs (MVIC-Q 40% of their body weight). Male KT candidates with PhA < 5.1° had poorer exercise capacity, lower muscle strength, less muscle mass, and smaller muscle size. A PhA < 5.1° was significantly associated with an eight-fold higher muscle weakness risk (OR = 8.2, 95%CI 2.3-29.2) in a binary regression model adjusted by age, frailty, and hydration status. Remarkably, PhA is an easily obtainable objective parameter in CKD patients, requiring no volitional effort from the individual. The associations of PhA with aerobic capacity, physical activity, muscle mass, and muscle size underscore its clinical relevance and potential utility in the comprehensive evaluation of these patients.

Phase Angle as a Risk Factor for Mortality in Patients Undergoing Peritoneal Dialysis

Phase angle (PhA) is measured using bioimpedance analysis and calculated using body reactance and resistance in the waveform at 50 kHz. Further studies are necessary to clarify the predictive efficacy of PhA in the mortality of peritoneal dialysis (PD) patients. The objective of this study was to assess the utility of PhA for predicting patient mortality and technique failure and compare the predictability of PhA with other risk factors. Our study had a retrospective cohort design. Our center routinely evaluates bioimpedance measurements for all prevalent PD patients (n = 199). The PhA was measured using multifrequency bioimpedance analysis. Our study evaluated patient and technique survival. There were 66, 68, and 65 patients in the low, middle, and high tertiles of PhA, respectively. The PhA values of the low, middle, and high tertiles were 3.6° (3.4-3.9), 4.4° (4.2-4.7), and 5.5° (5.2-6.0), respectively. The 5-year patient survival rates for the high, middle, and low tertiles were 100%, 81.7%, 69.9%, respectively (p < 0.001). The 5 year technique survival rates for the high, middle, and low tertiles were 91.9%, 74.8%, 63.7%, respectively (p = 0.004). Patient and technique survival increased as the PhA tertiles increased. Both univariate and multivariate Cox regression analyses demonstrated a consistent pattern. The prediction of patient or technique survival was better in PhA than in the other classical indicators. The present study demonstrated that PhA may be an effective indicator for predicting patient or technique survival in PD patients. Furthermore, it suggests that routine measurement of PhA and pre-emptive intervention to recover PhA according to causes of low PhA may help improve patient or technique survival in PD patients.

Low Phase Angle Values Are Associated with Malnutrition according to the Global Leadership Initiative on Malnutrition Criteria in Kidney Transplant Candidates: Preliminary Assessment of Diagnostic Accuracy in the FRAILMar Study

Malnutrition has a negative impact on patients with chronic diseases and its early identification is a priority. The primary objective of this diagnostic accuracy study was to assess the performance of the phase angle (PhA), a bioimpedance analysis (BIA)-derived parameter, for malnutrition screening using the Global Leadership Initiative for Malnutrition (GLIM) criteria as the reference standard in patients with advanced chronic kidney disease (CKD) waiting for kidney transplantation (KT); criteria associated with low PhA in this population were also analyzed. Sensitivity, specificity, accuracy, positive and negative likelihood ratios, predictive values, and area under the receiver operating characteristic curve were calculated for PhA (index test) and compared with GLIM criteria (reference standard). Of 63 patients (62.9 years old; 76.2% men), 22 (34.9%) had malnutrition. The PhA threshold with the highest accuracy was ≤4.85° (sensitivity 72.7%, specificity 65.9%, and positive and negative likelihood ratios 2.13 and 0.41, respectively). A PhA ≤ 4.85° was associated with a 3.5-fold higher malnutrition risk (OR = 3.53 (CI95% 1.0-12.1)). Considering the GLIM criteria as the reference standard, a PhA ≤ 4.85° showed only fair validity for detecting malnutrition, and thus cannot be recommended as a stand-alone screening tool in this population.

High abdominal adiposity and low phase angle in overweight renal transplant recipients

Obesity is associated with increased risk of cardiovascular disease (CVD). Body mass index (BMI) is the most used parameter for obesity screening. However, the evaluation of CVD risk in overweight individuals should include the assessment of body fat distribution and body composition. Renal transplant recipients (RTR) have a high CVD risk and frequently present weight gain and loss of lean mass. The aim of this study was to evaluate body fat distribution and body composition in overweight RTR. This cross-sectional study was conducted with 86 RTR and 86 hypertensive individuals (comparison group, CG) presenting BMI 25-35 Kg/m² and 45-70 years. Anthropometric evaluation included BMI, waist circumference, waist-to-height ratio, and a body shape index. Body composition was evaluated with bioelectrical impedance analysis (BIA). Glomerular filtration rate was estimated (eGFR) by CKD-EPI equation. RTR group (RTRG) and CG presented similar age and BMI. RTRG when compared to CG presented lower percentage of women and eGFR; higher central adiposity; and lower values of reactance, intracellular water, body cell mass and phase angle, more consistently observed in women. This study suggests that overweight RTR present higher abdominal adiposity and impairment in BIA parameters that are sensitive indicators of impaired membrane integrity, water distribution, and body cell mass.

Mitochondrial Activity and Skeletal Muscle Insulin Resistance in Kidney Disease

Insulin resistance is a key feature of the metabolic syndrome, a cluster of medical disorders that together increase the chance of developing type 2 diabetes and cardiovascular disease. In turn, type 2 diabetes may cause complications such as diabetic kidney disease (DKD). Obesity is a major risk factor for developing systemic insulin resistance, and skeletal muscle is the first tissue in susceptible individuals to lose its insulin responsiveness. Interestingly, lean individuals are not immune to insulin resistance either. Non-obese, non-diabetic subjects with chronic kidney disease (CKD), for example, exhibit insulin resistance at the very onset of CKD, even before clinical symptoms of renal failure are clear. This uraemic insulin resistance contributes to the muscle weakness and muscle wasting that many CKD patients face, especially during the later stages of the disease. Bioenergetic failure has been associated with the loss of skeletal muscle insulin sensitivity in obesity and uraemia, as well as in the development of kidney disease and its sarcopenic complications. In this mini review, we evaluate how mitochondrial activity of different renal cell types changes during DKD progression, and discuss the controversial role of oxidative stress and mitochondrial reactive oxygen species in DKD. We also compare the involvement of skeletal muscle mitochondria in uraemic and obesity-related muscle insulin resistance.

Pre, peri and posttransplant diabetes mellitus

PURPOSE OF REVIEW

The leading cause of death in both chronic kidney disease (CKD) and renal transplant patients is cardiovascular events. Post-transplant diabetes mellitus (PTx-DM), which is a major cardiovascular risk factor, is a metabolic disorder that affects 5.5-60.2% of renal allograft recipients by 1-year posttransplant (PTx). PTx-DM has been associated with a negative impact on patient and graft outcomes and survival.

RECENT FINDINGS

Individuals who develop PTx-DM are usually prone to this condition prior to and/or after developing CKD. Genetic factors, obesity, inflammation, medications and CKD all are risk factors for PTx-diabetes mellitus. The path to development of disease continues PTx frequently augmented by the use of diabetogenic maintenance immunosuppressive and some nonimmunosuppressive medications. These risk factors are usually associated with an increase in insulin resistance, a decrease in insulin gene expression and/or β-cell dysfunction and apoptosis.

SUMMARY

Some new anti-diabetes mellitus medications may help to improve the overall outcome; however, there is a real need for developing a preventive strategy. Identifying and targeting PTx-DM risk factors may help to guide the development of an effective programme. This could include the adoption of nondiabetogenic immunosuppressive protocols for high-risk patients.

Body composition changes differ by gender in stomach, colorectal, and biliary cancer patients with cachexia: Results from a pilot study

Few studies have examined the possibility that cachexia may affect men and women differently. This pilot study assessed gender differences in body composition in stomach, colorectal, and biliary cancer patients with cachexia. A sample of 38 participants (Female: Male = 17:21, mean age 57.4 years) were included if they were undergoing chemotherapy and experienced weight loss of 5% or more over a 6-month period. Bioelectrical impedance analysis (BIA) was applied to measure body composition. Phase angle (PA) and levels of extra-/intracellular water (ECW; ICW) were determined. Data were analyzed first by gender and then compared to age- and gender-matched healthy controls from the NHANES-III dataset. PA was lower (P < .01) in both genders compared with healthy controls, and PA was lower in female patients compared with male patients (P = .03). Male cancer patients with lower PA also had lower ICW levels compared with healthy controls (r = .98, P < .01). For female patients, PA and ICW were negatively correlated (r = .897, P < .01). A lower ECW/ICW ratio was highly correlated (r = .969 for men, r = .639 for women) with increased PA in cancer patients. ICW changes are gender-specific in patients with GI cancer. ECW/ICW ratios and PA may be suitable surrogate markers for gender-specific changes in cell composition and health status.

Hydration and nutritional status in patients on home-dialysis-A single centre study

BACKGROUND

Over-hydration (OH) and malnutrition are prevalent among patients on dialysis therapy. The prevalence of OH and malnutrition as well as the risk factors associated with OH and malnutrition in our patients on home peritoneal dialysis (PD) and home haemodialysis (HD) are examined.

DESIGN AND METHODS

This was a cross-sectional study. The hydration and nutritional status of the study groups were assessed by a Body Composition Monitor. Patients who were stable on home dialysis therapy for over one year were invited to participate. Univariate and multivariate analyses were performed to identify associated factors and determine the predictors of OH and malnutrition, respectively.

RESULTS

Eighty-eight patients (41 PD and 47 home HD) were recruited. A 32.95% of our patients on home dialysis therapy were in OH status. There was a significance difference in the prevalence of hydration status between patients on PD and home HD (p = 0.014), as overhydration was more common in patients on PD than home HD (46.34 vs. 21.28%). Dehydration was more common in patients on home HD than PD (29.79 vs. 9.76%). Male gender, decreasing haemoglobin level and presence of diabetes mellitus (DM) were risk factors of OH on multivariable analysis. There was no significance difference in the prevalence of malnutrition between patients on PD and home HD (p = 0.27). Increasing Fat Tissue Index (FTI), height and patients on PD therapy were at higher risk of malnutrition.

CONCLUSION

OH and malnutrition were prevalent patients on home dialysis therapy.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

Lean Body Mass and Survival in Hemodialysis Patients and the Roles of Race and Ethnicity

BACKGROUND

Lean body mass (LBM) represents the "fat-free" muscle mass in hemodialysis (HD) patients and is an important nutritional measure. Previous studies have found that both higher LBM and body mass index (BMI) were related to greater survival in HD patients. Additional studies have shown differences in survival across racial-ethnic groups of HD patients. However, the association of LBM and mortality across racial-ethnic subgroups has not been examined.

OBJECTIVE

We hypothesize that racial differences in LBM affect the mortality in HD patients.

SETTING AND SUBJECTS

Chronic HD patients from a large dialysis organization in the United States.

PREDICTORS

Estimated LBM (eLBM), self-identified racial subgroups.

MAIN OUTCOME MEASURE

5-year survival.

STUDY DESIGN

We examined the association between baseline eLBM and survival using Cox proportional hazard models adjusted for demographics, comorbidities, and laboratory measures. Associations were examined across subgroups of race-ethnicity (non-Hispanic white, African American, and Hispanic) and BMI.

RESULTS

The final cohort included 117,683 HD patients, who were 62 ± 15 (mean ± standard deviation) years old, 43% women and 59% with diabetes mellitus. Higher eLBM was linearly associated with lower mortality. Compared with the reference group (48.4-<50.5 kg), patients with the lowest eLBM (<41.3 kg) had a 1.4-fold higher risk of mortality (hazard ratio: 1.37; 95% confidence interval: 1.30-1.44) in the fully adjusted model. A similar linear association was seen among patients with BMI < 35 kg/m(2) and in non-Hispanic whites and African American subgroups. However, higher eLBM was not associated with improved survival in Hispanic patients or patients with BMI ≥ 35 kg/m(2).

LIMITATION

Potential residual confounding.

CONCLUSIONS

Higher eLBM is associated with a lower mortality risk in HD patients, especially among non-Hispanic white and African American groups. Hispanic patients do not demonstrate a similar inverse relationship. The association between LBM and mortality among different racial groups of HD patients deserves additional study.

Body Composition Affects Urea Distribution Volume Estimated by Watson's Formula

OBJECTIVE

Dialysis machines use the Watson formula (Vwatson) to estimate the urea distribution volume (UDV) to calculate the online Kt/V for each dialysis session. However, the equation could give rise to inaccuracies. The present study analyzes whether body composition affects UDV estimated by Vwatson in comparison to bioimpedance spectroscopy (Vbis) as the reference method.

DESIGN

This is a transversal study performed in the setting of a hemodialysis unit.

SUBJECTS

Prevalent hemodialysis patients.

INTERVENTION

The same day, UDV was measured using Vwatson and Vbis. We compared their results.

MAIN OUTCOME MEASURE

Differences between UDV using Watson equation and Vbis.

RESULTS

We included 144 prevalent patients. Vwatson overestimated the volume with regard to Vbis (Vwatson - Vbis) by 2.5 L (1.8 L; P = .001). We found an excellent correlation between the 2 methods. A higher mean Vwatson - Vbis value was correlated to older age (P = .03), body mass index (P = .01), fat tissue index (P = .001), lower lean tissue index (P = .001), lower extracellular water (P = .01), and intracellular water (P = .001).

CONCLUSION

Body composition affects UDV estimated by Vwatson, thus modifying the result of Kt/V. In young patients who present more lean tissue and less fat tissue, Kt/V is underestimated with Vwatson.

The relationship between glutathione peroxidase and bioimpedance parameters in nondiabetic hemodialysis patients

There is growing evidence from experimental and clinical studies that oxidative stress is involved in the pathogenesis of malnutrition. This cross-sectional study aimed to investigate the relationship between glutathione peroxidase (GPx) levels as a marker of antioxidant status and the nutritional status assessed by bioimpedance analysis (BIA). Ninety-seven nondiabetic stable outpatient uremic adults undergoing chronic hemodialysis (HD) were recruited for this study. Impedance measurements were performed using a multifrequency bioelectrical impedance analyzer after dialysis. GPx levels correlated with intracellular water (ICW) (r = 0.341, P = 0.011), ICW/total body weight (r = 0.320, P = 0.017), lean body mass (r = 0.300, P = 0.026) and total body cell mass (r = 0.339, P = 0.011). When patients were divided into two groups according to mean GPx levels (83.9 U/gr hemoglobin), the patients with higher GPx (GPx > 83.9 U/gr hemoglobin) had higher albumin (P = 0.038), lean body mass (P = 0.026), ICW (P = 0.011), and total body cell mass (P = 0.011) compared with those with lower GPx (GPx ≤ 83.9 U/gr hemoglobin). Furthermore, in the patients with higher GPx, body fat; extracellular water/total body water; illness marker and body fat mass index were lower than other group. In conclusion, our results reveal correlation indicating a relationship between antioxidant status (as measured by GPx) and nutritional status as assessed by BIA in nondiabetic HD patients.

Comparison of nutritional parameters among adult and elderly hemodialysis patients

AIM

The aim of this study was to compare the nutritional biochemical parameters, prealbumin levels, and bioimpedance analysis parameters of adult and elderly hemodialysis (HD) patients.

METHODS

This prospective cross-sectional study included 50 adult HD patients (42.0 % female). Nutritional status was assessed by post-dialysis multifrequency bioimpedance analysis (BIA), serum prealbumin and other nutritional biochemical parameters.

RESULTS

Mean age of patients was 57.4±15.1 years (range: 30-83 years) and mean dialysis duration was 68.3 ± 54.5 months (range: 3-240 months). When the patients were divided into two groups according to age of patients (<65 and ≥65), prealbumin (p=0.003), blood urea nitrogen (BUN) (p=0.000), serum creatinine (p=0.013), albumin (p=0.016), protein catabolic rate per normalized body weight (nPCR) (p=0.001), intracellular water (ICW)/total body weight (0.003) , body fat mass (p00.000), lean body mass (p=0.031), lean dry mass (p=0.001), illness marker (p=0.005), basal metabolism (p=0.007), body mass index (BMI) (p=0.028), body fat mass index (BFMI) (p=0.000), fat free mass index (FFMI) (p=0.040) values were significantly different between the groups. In the elderly patients (age ≥65), body fat mass, illness marker, BMI, BFMI were higher compared to adult patients (age <65). Additionally, in the elderly patients, prealbumin, BUN, creatinine, albumin, nPCR, ICW/ total body weight, lean body weight, lean dry weight, basal metabolism and FFMI were lower than adult patients.

CONCLUSIONS

Our results indicate that BFMI were higher, albumin, prealbumin, nPCR and lean body mass and FFMI were lower in elderly patients compared to adults. These results imply that elderly HD patients may be prone sarcopenic obesity and may require special nutritional support.

Survival predictability of lean and fat mass in men and women undergoing maintenance hemodialysis

BACKGROUND

Larger body size is associated with greater survival in maintenance hemodialysis (MHD) patients. It is not clear how lean body mass (LBM) and fat mass (FM) compare in their associations with survival across sex in these patients.

OBJECTIVE

We examined the hypothesis that higher FM and LBM are associated with greater survival in MHD patents irrespective of sex.

DESIGN

In 742 MHD patients, including 31% African Americans with a mean (± SD) age of 54 ± 15 y, we categorized men (n = 391) and women (n = 351) separately into 4 quartiles of near-infrared interactance-measured LBM and FM. Cox proportional hazards models estimated death hazard ratios (HRs) (and 95% CIs), and cubic spline models were used to examine associations with mortality over 5 y (2001-2006).

RESULTS

After adjustment for case-mix and inflammatory markers, the highest quartiles of FM and LBM were associated with greater survival in women: HRs of 0.38 (95% CI: 0.20, 0.71) and 0.34 (95% CI: 0.17, 0.67), respectively (reference: first quartile). In men, the highest quartiles of FM and percentage FM (FM%) but not of LBM were associated with greater survival: HRs of 0.51 (95% CI: 0.27, 0.96), 0.45 (95% CI: 0.23, 0.88), and 1.17 (95% CI: 0.60, 2.27), respectively. Cubic spline analyses showed greater survival with higher FM% and higher "FM minus LBM percentiles" in both sexes, whereas a higher LBM was protective in women.

CONCLUSIONS

In MHD patients, higher FM in both sexes and higher LBM in women appear to be protective. The survival advantage of FM appears to be superior to that of LBM. Clinical trials to examine the outcomes of interventions that modify body composition in MHD patients are indicated.

The phase angle and mass body cell as markers of nutritional status in hemodialysis patients

OBJECTIVE

Bioelectrical impedance analysis (BIA) is a fast, noninvasive method for assessing body composition, and its role in the evaluation of nutritional status in haemodialysis (HD) has been studied. This study aimed to compare BIA parameters to clinical, biochemical, and anthropometric markers of nutrition in HD patients, such as subjective global assessment modified for renal disease (SGA-1), serum albumin, body mass index (BMI), percent of standard body weight (%SBW), deviation of triceps skinfold thickness (TSF), mid-arm circumference (MAC), mid-arm muscle circumference (MAMC) from the standard value (50th percentile), anthropometry-derived fat (FM-A), and fat-free mass (FFM-A).

METHODS

BIA was performed 30 minutes after a HD session and the reactance (Xc), resistance (R), phase angle (PA), body cell mass (BCM), fat mass (FM-BIA), and fat-free mass (FFM-BIA) values were recorded. The prevalence of malnutrition was estimated according to PA and percent of BCM. The correlation between methods was assessed through Pearson's correlation coefficient and Bland and Altman analysis.

RESULTS

A total of 58 patients were studied (30 women and 28 men; mean age of 49.2 +/- 14.8 years). The mean PA was 6.19 +/- 1.33 degrees and the mean percent of BCM was 33.75 +/- 5.91%. The prevalence of malnutrition was 17.5% and 43.9% according to the PA and percent of BCM, respectively. PA had a negative correlation with age and SGA-1 score and a positive correlation with percent SBW, MAC, MAMC, FFM-A, and albumin. Percent of BCM had a negative correlation with age, MAC, MAMC and FM-A and a positive correlation with FFM-A and albumin. A significant correlation between FFM-A and FFM-BIA was observed, as well as between FM-A and FM-BIA.

CONCLUSIONS

BIA indexes reflected nutritional state. PA and BCM seem to be less influenced by changes in volume and can be used for nutritional assessments of dialysis patients.

Population pharmacokinetic model for human growth hormone in adult patients in chronic dialysis compared with healthy subjects

OBJECTIVE

To develop a population pharmacokinetic (PK) model of recombinant human growth hormone (rhGH) treatment in patients with end-stage renal disease (ESRD) and healthy volunteers (HVs), to support future study design.

DESIGN

This was an open, non-randomized, single-centre parallel-group study lasting 8-9 days. Various compartment models with first-order and Michaëlis-Menten absorption and elimination were explored. Eleven adult ESRD patients and 10 matched HVs received 50 microg/kg/day rhGH (subcutaneous (s.c.) injection) for 8 or 7 days, respectively. Blood samples were drawn every 30 min for 24h following dosing on Days 0, 7 and 8 (ESRD patients). Influence of the covariates subject group (ESRD/HV), gender, weight, and dialysis flow-rate on model parameters was examined.

RESULTS

The final model was one-compartmental with Michaëlis-Menten absorption and elimination. The following estimates were obtained: maximum absorption rate (VMA) - 11.3 microg/kg/h (both groups); amount of drug corresponding to half-maximum absorption rate (KMA) - 1.06 and 18.8 microg/kg (ESRD patients and HVs, respectively; P<0.001); maximum elimination rate (VM) - 9.37 and 13.0 microg/kg/h (ESRD patients and HVs, respectively; P<0.001); amount of drug corresponding to half-maximum elimination rate - 18.9 microg/kg (both groups). Significant differences in KMA and VM between HVs and ESRD patients corresponded to higher absorption and lower elimination rates in ESRD, but all GH profiles were back to baseline by 20-22h and no overall accumulation occurred. Simplified posterior predictive checks indicated that the model satisfactorily captured PK. All non-compartmental estimates for AUC(0-24h) and C(max) lay within 95% confidence limits of the simulated distributions.

CONCLUSIONS

A population PK model was established, which showed acceptable performance for trial-simulation purposes.

Association between body mass index and body fat in chronic kidney disease stages 3 to 5, hemodialysis, and peritoneal dialysis patients

OBJECTIVE

Chronic kidney disease (CKD) patients may present with altered body composition. Body mass index (BMI) is a simple method for evaluating body fat mass (FM) in the general population. In CKD patients, there are few reports demonstrating the association between BMI and body composition. Our objective was to investigate the reliability of BMI as an indicator of FM in patients with CKD stages 3 to 5.

METHODS

Seventy-eight nondiabetic CKD patients (aged 48, SD +/- 12 years; 45% male) and 30 healthy control subjects (aged 46, SD +/- 12 years; 40% male), matched for age and sex, were evaluated. Chronic kidney disease patients were divided, according to K/DOQI guidelines, into 27 subjects at stages 3 to 4 (mean glomerular filtration rate of 43 +/- 12 mL/minute; age, 52 +/- 10 years), and 51 at stage 5: 25 in hemodialysis (HD) (aged 45, SD +/- 12 years; 44% male), and 26 in peritoneal dialysis (PD) (aged 49, SD +/- 13 years; 42% male). Body mass index was calculated as weight/height(2), and body composition was evaluated through dual-energy x-ray absorptiometry.

RESULTS

There was no difference in median BMI (kg/m(2)) among healthy control subjects (24.8; range, 19.2-34.1), CKD stages 3 to 4 (26.4; range, 20.4-37.6), HD patients (24.5; range, 19.4-35.7), and PD patients (24.5; range, 20.2-37.7; P > .05). Likewise, no significant difference was verified in median body FM (kg) among control subjects (18.8; range, 9.2-36.5), CKD stages 3 to 4 (21.2; range, 11.6-37.9), HD patients (17.1; range, 4.8-38.9), and PD patients (20.1; range, 6.5-41.5; P > .05). Moreover, a positive and significant correlation was found between BMI and FM (kg) in CKD stages 3 to 4 (Rho = 0.67, P = .0002), in HD patients (Rho = 0.67, P = .0002), in PD patients (Rho = 0.79, P < .0001), and in control subjects (Rho = 0.79, P < .0001). Although BMI and lean body mass (in kg) was significantly correlated in CKD stages 3 to 4 (Rho = 0.58, P = .001) and healthy control subjects (Rho = 0.30, P = .007), no significant correlation was found in HD patients (Rho = 0.19, P = .34) and in PD patients (Rho = 0.17, P = .38).

CONCLUSIONS

Body composition did not differ in patients with CKD stages 3 to 5, and between dialysis modalities. Although BMI was strongly and significantly correlated with body FM in CKD patients at stages 3 to 5, lean body mass was not. These findings suggest that BMI is a reliable indicator of body FM in this CKD population.

Increased body mass index is not a reliable marker of good nutrition in hemodialysis patients

OBJECTIVE

The aim of the study was to assess the body fat (BF) composition in hemodialysis (HD) patients using anthropometry and bioelectrical impedance analysis (BIA) and investigate relationships between BIA-determined BF composition and nutritional parameters in different weight groupings.

DESIGN

Cross-sectional study.

SETTING

A tertiary-care university hospital.

METHODS

164 HD patients (M/F: 89/75, mean age: 48.4 +/- 15.8 years, mean HD duration: 58.2 +/- 42.6 months) were divided into three groups according to body mass index (BMI): normal weight (NW: BMI 18.5-24.9), overweight (OW: BMI 25-29.9), obese (OB, BMI > or = 30). Biochemical parameters and BF composition using anthropometry and foot-to-foot BIA were compared between three groups.

RESULTS

Ninety-six (59%) patients were NW, 40 (24%) were OW, and 28 (17%) were OB. Average mean skinfold thickness (p = 0.005), mid-arm circumference (p = 0.001), BF% (p = 0.001), and fat-free mass (FFM) (p = 0.03) were all significantly greater in the OB group than in the NW group. Compared to the NW patients, the OB group had significantly higher serum levels of glucose (p = 0.03), total cholesterol (p = 0.02), and triglycerides (p = 0.02), but significantly lower serum albumin (p = 0.05) and blood urea nitrogen (p = 0.05). The OB group also had significantly higher white blood cell count (p = 0.002) and serum CRP (p = 0.001) than the NW group.

CONCLUSIONS

The results suggest that BIA-determined BF composition is correlated with body mass index. In addition, obesity is associated with elevated CRP and white blood cell count and lower serum albumin level in HD patients.

The altered fluid distribution in obesity may reflect plasma hypertonicity

OBJECTIVE

This study explored whether the increased extracellular relative to intracellular fluid (ECF/ICF) ratio in obesity might reflect osmotic effects of elevated plasma solute concentrations.

DESIGN

Cross-sectional, epidemiological survey.

SETTING AND SUBJECTS

The present analysis used nationally representative data from the Third National Health and Nutrition Examination Survey on community-dwelling adults (aged 40-59 years) in the US without evidence of glucose dysregulation or chronic disease (n=1285).

INTERVENTION

Body mass index (BMI) was estimated from measured height and weight. Total body reactance, an index of body fluid distribution, was determined by bioelectrical impedance analysis. Plasma tonicity (the cumulative index of osmotically effective plasma solute) was estimated from plasma glucose, sodium and potassium. Sex-specific relative odds of lower reactance (<or=50 Omega/m for women, <or=40 Omega/m for men) and plasma hypertonicity (tonicity >or=295 mmol/l) associated with overweight (25<or=BMI <30) and obesity (BMI>or=30) were estimated using logistic regression models that controlled for sociodemographic variables, smoking, leisure-time physical activity, total energy intake, serum creatinine, plasma insulin and glucose. Multinomial logistic regression models tested for associations between weight status and specific serum solute.

RESULTS

Independent of covariates, in men and women, overweight and obesity were associated with increased odds of lower reactance and hypertonicity. Overweight and obese individuals with lower reactance had significantly higher serum sodium than normal weight individuals.

CONCLUSIONS

Elevated plasma solute concentrations are associated with obesity in free-living adults. Physicians and researchers should be alert to a possible link between hypertonicity and obesity.

SPONSORSHIP

Grants from the NIH, Nestle Waters.

Prospective nutritional surveillance using bioelectrical impedance in chronic kidney disease patients

Malnutrition is a well-known risk factor influencing survival in chronic maintenance dialysis patients. Chronic kidney disease (CKD) patients are also predisposed to malnutrition because of dietary restrictions and the catabolic effects of uremia. Therefore, a significant degree of malnutrition may be present before the initiation of renal replacement therapy. We consequently initiated a prospective evaluation of subjects attending the CKD clinic, where all patients are seen by a renal dietitian and nutritional, biochemical, and bioimpedance parameters are measured every 3 months. A total of 40 patients have completed 9 months of follow-up and are the subject of this report. Their mean age is 65 +/- 12 years, 48% female, 68% black, and 58% diabetic patients. The glomerular filtration rate did not change during follow-up (36 +/- 12 versus 34 +/- 14 mL/min/1.72 m 2 , at baseline and 9 months, respectively). Similarly, no differences between baseline and 9 months were noted in weight (88.0 +/- 20.3 versus 86.8 +/- 18.7 kg, respectively) or body mass index (30.6 +/- 5.8 versus 30.2 +/- 5.4 kg/m 2 , respectively). In addition, no differences between baseline and 9 months were noted in total body water (44.4 +/- 11.4 versus 44.6 +/- 10.8 L, respectively), body cell mass (25.3 +/- 7.4 versus 25.2 +/- 7.0 kg, respectively), and fat-free mass (59.2 +/- 16.6 versus 59.4 +/- 15.7 kg, respectively). The bioimpedance vector decreased with time in 25 subjects (62%), indicating a state of overhydration. Subjects were further analyzed by vector category. Body cell mass did not change in either group. As expected, total body water increased in the group with a decreasing bioimpedance vector. Because body cell mass did not increase, the greater total body water reflected an increase in extracellular volume (edema). In the group with stable vectors, no changes were noted with time in weight or total body water. These results indicate that CKD patients with stable renal function following a judicious dietary protein intake (0.6 to 0.8 g/kg normalized body weight/day) have no loss of body cell mass or fat-free mass over a 9-month period. Of note, a high proportion of patients (62%) developed clinically unrecognized fluid retention, which is promptly identified by a decreasing bioimpedance vector.

Body composition analysis with bioelectric impedance in adult Indians with ESRD: Comparison with healthy population

Evaluation of body composition provides clinically useful information in several diseases including chronic kidney disease. Bioimpedance analysis (BIA) is a simple, cheap, and noninvasive tool for monitoring body composition. We performed BIA in 451 healthy adults and 162 end-stage renal disease (ESRD) patients. Resistance (R) and reactance (Xc) values were obtained at 50-kHz frequency using a tetrapolar impedance meter. Body compartments were derived using population-specific regression equations. Phase angles (arctan Xc/R) were calculated and impedance vector distribution was determined using the RXc graph method. Compared to healthy population, ESRD patients had similar post-dialysis resistance with lower reactance and phase angle, indicating decreased soft tissue mass and inadequate ultrafiltration. BIA equations estimated decreased fat mass index and intracellular water, whereas the total body and extracellular water percentages were increased. Sex-specific reference RXc plots with 95, 75, and 50% tolerance ellipses were drawn for the healthy population. A significant difference was noted in the vector positions and 95% confidence ellipses of the two sexes and body mass indices of </=25 and >25. In conclusion, we present the reference BIA parameters for Indian population. ESRD patients show significant body compartment alterations. The RXc score graph can differentiate ESRD patient from normal controls and can be used to monitor nutrition and hydration status.

Estimate of body water compartments and of body composition in maintenance hemodialysis patients: comparison of single and multifrequency bioimpedance analysis

OBJECTIVE

The goal of this study was to compare the adequacy of single and multifrequency bioimpedance analysis (BIA) to evaluate body water compartments, body composition, and nutritional status in maintenance hemodialysis patients.

DESIGN

Cross-sectional study.

SETTING

University-based hemodialysis unit.

PATIENTS

Nineteen patients (12 male, 7 female), ages 28 to 82 years (mean, 58.9), treated with maintenance hemodialysis (MHD) for 0.5 to 15 years (mean, 7.3).

INTERVENTION

This was a noninterventional study. Patients gave their informed consent to the diagnostic procedures performed.

MAIN OUTCOME MEASURES

Total body water (TBW), extracellular water (ECW), fat-free mass (FFM), and body cell mass (BCM) volumes were estimated with single-frequency (sf BIA) and multifrequency (mf BIA) plethysmographs before and after a midweek dialytic session. Predialysis TBW also was estimated from anthropometric data (e TBW). Serum albumin, prealbumin and myoglobin, and creatinine index were determined as indicators of nutritional status and muscle mass.

RESULTS

Sf BIA and mf BIA gave very similar results for TBW volumes. A high linear correlation was also found between e TBW values and both sf TBW and mf TBW; however, a statistically significant difference was found between e TBW and sf and mf TBW. Sf BIA and mf BIA gave quite different results for ECW, particularly when measured predialysis. The results obtained for FFM indicate a poor agreement between sf and mf BIA. The agreement was better when FFM was measured postdialysis. The values of BCM, either measured predialysis or postdialysis, indicate a significant difference between sf and mf BIA. FFM and BCM estimated with mf BIA had a closer correlation with creatinine index than sf BIA. mf BCM had also a higher correlation with serum myoglobin, which is produced by muscle cells.

CONCLUSIONS

TBW can be estimated with enough confidence from either sf or mf BIA at any time. On the contrary, the results of ECW are significantly different with sf and mf BIA when measured predialysis. Thus, it seems more convenient to perform BIA after dialysis, in particular when assessing the "ideal" body weight. The measurements of FFM and BCM, obtained with either sf or mf BIA, are correlated with different indicators of nutritional status. In particular, mf BCM seems more appropriate than sf BCM for estimating muscle mass.

Comparison of anthropometric data between end-stage renal disease patients undergoing hemodialysis and healthy adults in Korea

Protein-calorie malnutrition is prevalent in hemodialysis (HD) patients. The prevalence of obesity in healthy Korean adults has increased rapidly during the last 10 years. However, there are few large scale data collections available about the current weight status of Korean HD patients. The weight statuses of 10,304 HD patients (data from the Insan Memorial Dialysis Registry 2002, Korean Society of Nephrology) were compared to those of 12,436 control subjects (age > 18) by using body mass index (BMI). Weight status was assessed by WHO classification for Asian-Pacific region [underweight (UW): < 18.5; normal weight (NW): 18.5-22.9; overweight (OW): 23-24.9; obese (OB): 25-29.9; and extremely obese (EOB): > 30 kg/m2] in both the control and HD patients. HD patients had significantly lower body weight and BMI than the controls in all age groups and in both sexes. For the male controls, the proportions of OW and OB showed a reversed U-shape, peaking at the 5th and 6th decades. of the numbers of those classified as NW and UW were relatively small. For the female controls, the proportions of OW and OB progressively increased with age. On the contrary, in HD patients, the proportions of NW and UW were large, up to more than 70%, and those of OW and OB were small in both sexes. In each age group, UW was seen significantly more in the HD group than in the control group. The 6th decade age group showed the highest prevalence ratio for UW in the HD group for both sexes, compared to the controls (Male: 17.33, Female: 17.68). The percentages of UW were related to HD duration and age in both sexes. In conclusion, Korean HD patients seem to have small proportions of OW and OB, compared to the general population, and protein-calorie malnutrition may still be an important nutritional condition.

High prevalence of plasma hypertonicity among community-dwelling older adults: results from NHANES III

OBJECTIVE

Recent data suggest that as many as 50% of older adults may have hypertonic plasma, an indicator of cell dehydration that predicts a range of adverse outcomes. To determine if a prevalence of this magnitude could be real, this study used nationally representative data to estimate the prevalence of hypertonicity, and to test for biologically plausible associations between hypertonicity, older age, glucose dysregulation, hemoconcentration, reduced bioelectrical impedance, and water intake.

DESIGN

Cross-sectional.

SUBJECTS

Community-dwelling adults (aged 20 to 90 years) who gave blood as part of the Third National Health and Nutrition Examination Survey (N = 14,855).

STATISTICAL ANALYSES

Plasma tonicity was estimated from glucose, sodium, and potassium values. The weighted prevalences of mild (295 to 300 mmol/L) and overt hypertonicity (> or = 300 mmol/L) were estimated by age, sex, race/ethnicity, fasting, and glycemic status. Hyper- and normotonic (285 to 295 mmol/L) groups were compared with respect to elevated blood chemistry values, bioelectrical impedance analysis parameters, as well as total water intake (grams, % Adequate Intake, and grams per kilogram body weight), using multivariable models that adjusted for age, sex, race/ethnicity, and survey design.

RESULTS

Mild and overt hypertonicity were observed in 40% and 20% of the sample, respectively. Hypertonicity was positively associated with older age, Hispanic and African-American race, impaired glucose tolerance, diabetes, and hemoconcentration, and inversely associated with bioelectrical impedance analysis parameters. Hypertonicity was associated with greater total water intake in younger adults, but decreased intake in older adults.

CONCLUSIONS

Clinicians and researchers should be alert to hypertonicity and its causes in older adults.

Bioelectrical impedance analysis in clinical practice: a new perspective on its use beyond body composition equations

PURPOSE OF REVIEW

The bioelectrical impedance analysis is not a direct method for estimating body composition. Its accuracy depends on regression equations, and recent papers have suggested that this approach should not be used in several clinical situations. Another option is to obtain information about the electrical properties of tissues by using raw bioelectrical impedance measurements, resistance and reactance. They can be expressed as a ratio (phase angle) or as a plot (bioelectrical impedance vector analysis). This review describes their use in clinical practice.

RECENT FINDINGS

The phase angle changes with sex and age. It is described as a prognostic tool in many clinical situations. There are some controversies about considering it as a nutritional marker. Studies in burn victims and sickle-cell disease corroborate its ability to evaluate cell membrane function. Bioelectrical impedance vector analysis allows a semi-quantitative estimation of body composition from information from tissue hydration and soft-tissue mass in a plot. It can be used in healthy individuals or patients, for a population or individual evaluation of fluid imbalance or an assessment of soft-tissue mass. It has also been used as a prognostic tool in dialysis and cancer patients.

SUMMARY

The phase angle can be considered a global marker of health, and future studies are needed to prove its utility in intervention studies. Bioelectrical impedance vector analysis has increased its utility in clinical practice, even when the equations may be inaccurate for body composition analysis.

Adipose tissue cytokines, insulin sensitivity, inflammation, and cardiovascular outcomes in end-stage renal disease patients

From an evolutionary perspective, Darwinian selection has favored insulin-resistant individuals, ie, those with a trait ensuring brain functioning in situations of extreme fuel deprivation. The ability to mount a powerful inflammatory response to infection was another survival advantage in our ancestors, and we now have solid evidence showing that these 2 traits, insulin resistance and inflammation (as measured by serum C-reactive protein [CRP]), are associated in modern human beings. In an analysis of 192 nondiabetic hemodialysis patients, leptin and adiponectin were related in an opposite fashion with insulin sensitivity in end-stage renal disease (ESRD) and interacted in determining insulin resistance in these patients. The risk of insulin resistance was about 6 times higher in ESRD patients with an unfavorable combination of the 2 adipokines (high leptin and low adiponectin) than in those with a favorable combination (low leptin and high adiponectin). Low adiponectin but not high leptin predicted incident cardiovascular events in this cohort. Neither leptin nor adiponectin were associated with CRP in a cross-sectional analysis, but they were linked in an opposite fashion to CRP in a longitudinal study in 21 patients with acute inflammation secondary to infection. High sympathetic activity predicts adverse cardiovascular outcomes in ESRD. Of note, we found that the risk for cardiovascular events is more than 3 times higher in patients with high sympathetic activity and low adiponectin than in those with high adiponectin and low sympathetic activity. The adipocyte hormones leptin and adiponectin are associated in an opposite fashion to insulin sensitivity and inflammation in ESRD patients. Relatively lower plasma adiponectin levels are associated with a higher rate of incident cardiovascular events. Finally, low adiponectin and high norepinephrine seem to be interacting factors in the dismal cardiovascular outcomes with ESRD.

Best Method for Estimating Urea Volume of Distribution: Comparison of Single Pool Variable Volume Kinetic Modeling Measurements with Bioimpedance and Anthropometric Methods

The urea volume of distribution (Vurea) is a key component of the Kt/V parameter calculated during urea kinetic modeling. The Vurea parameter has been approximated empirically using total body water (TBW) estimates derived from anthropometric formulas or measured by bioelectric impedance analysis (BIA). The author compared TBW values derived using various anthropometric formulas (Watson, Hume, Randall, Tzamaloukas, Chertow) and BIA to the Vurea parameter calculated using three point variable volume single pool urea kinetic modeling. A total of 127 chronic hemodialysis patients were studied (mean age 66 +/- 13 years; 42% female; 37% black; 47% diabetic). Agreement between anthropometric formulas, BIA, and Vurea values was assessed by linear regression and Bland Altman analyses. The closest correlations were obtained with the BIA (r = 0.972), Chertow (r = 0.917), and Tzamaloukas (r = 0.905) methods. When compared with Vurea, 95% confidence intervals by Bland Altman analysis were lowest with BIA (4L) and highest with the Watson method (8L). These results indicate that BIA best approximates Vurea in dialysis patients.

Relationship of bioelectrical impedance parameters to nutrition and survival in peritoneal dialysis patients

BACKGROUND

Malnutrition is highly prevalent in peritoneal dialysis (PD) patients and is associated with higher mortality in these patients. In this study, we have prospectively examined the relationship of bioimpedance indexes to the nutritional status and survival in PD patients.

METHODS

We enrolled 48 PD patients beginning in November 2000. On enrollment, bioelectrical impedance analysis (BIA) (BIA-101; RJL/Akern, Clinton Township, MI, USA) was performed and monthly blood was analyzed for biochemical markers, including prealbumin. Patients were followed until April 2003.

RESULTS

The mean age of PD patients was 51 +/- 15 (SD) years. Fifty-eight percent of the patients were female and 23% of the patients were diabetic. Mean body mass index (BMI) was 25.7 +/- 5.0 kg/m2. Mean resistance, reactance, and phase angle were 521 +/- 104 ohms, 57 +/- 19 ohms, and 6.16 +/- 1.6 degrees, respectively. During the study period, 8 patients (17%) expired. The Kaplan-Meier method was used to compute observed survival. The cumulative observed survival of PD patients with enrollment phase angle greater than or equal to 6 degrees was significantly higher (P = 0.008) than that of patients with phase angle less than 6. Using Cox's multivariate regression analysis, phase angle was an independent predictor (relative risk = 0.39, P = 0.027) of more than two years' survival in PD patients. Serum prealbumin was directly correlated with phase angle (r = 0.54, P < 0.0001), reactance (r = 0.55, P < 0.0001), and resistance (r = 0.29, P = 0.06).

CONCLUSION

BIA indexes reflect nutritional status and may be useful in monitoring nutritional status in PD patients. Phase angle is a strong prognostic index in PD patients. It is useful to incorporate prealbumin and BIA parameters in the regular assessment of PD patients, whose survival may be improved by better management of malnutrition and overall health status.