Agreement Between Anthropometry and Bioelectrical Impedance for Measuring Body Fat in Nonobese and Obese Nondialyzed Chronic Kidney Disease Patients

Body Fat Analysis in Predialysis Chronic Kidney Disease: Multifrequency Bioimpedance Assay and Anthropometry Compared With Dual-Energy X-Ray Absorptiometry

OBJECTIVES

Body composition analysis is required for accurate assessment of nutritional status in patients with predialysis chronic kidney disease (CKD). The reference method for assessing body fat is dual-energy X-ray absorptiometry (DXA), but it is relatively expensive and often not available for widespread clinical use. There is only limited data on the utility of less expensive and easily available alternatives such as multifrequency bioimpedance assay (BIA) and skinfold thickness (SFT) measurements for assessing body fat in predialysis CKD. The study intends to assess the utility of BIA and SFT in measuring body fat compared to the reference method DXA in subjects with predialysis CKD.

METHODS

Body composition analysis was done in 50 subjects with predialysis CKD using multifrequency BIA, SFT, and DXA. The agreement between the body fat percentages measured by reference method DXA and BIA/SFT was assessed by paired t-test, intraclass correlation coefficients (ICCs), regression, and Bland-Altman plots.

RESULTS

Percentage of body fat measured by BIA was higher compared to the measurements by DXA, but the difference was not significant (30.44 ± 9.34 vs. 28.62 ± 9.00; P = .071). The ICC between DXA and BIA was 0.822 (confidence interval: 0.688, 0.899; P = .000). The mean values of body fat percentages measured by anthropometry (SFT) was considerably lower when compared to DXA (23.62 ± 8.18 vs. 28.62 ± 9.00; P = .000). The ICC between DXA and SFT was .851 (confidence interval: 0.739, 0.915; P = .000). Bland-Altman plots showed that BIA overestimated body fat by a mean of 1.8% (standard deviation, 6.98), whereas SFT underestimated body fat by 5% (standard deviation, 4.01). Regression plots showed a better agreement between SFT and DXA (R(2) = .79) than BIA (R(2) = .50). Overall, SFT showed better agreement with the DXA. Body mass index (BMI) showed a moderate positive correlation with body fat measured by DXA whereas serum albumin failed to show good correlation.

CONCLUSIONS

SFT showed relatively better agreement with the reference method DXA, compared to BIA. SFT can be used as a tool for assessing nutritional status in predialysis patients with CKD.

Urinary creatinine excretion, bioelectrical impedance analysis, and clinical outcomes in patients with CKD: the CRIC study

BACKGROUND AND OBJECTIVES

Previous studies in chronic disease states have demonstrated an association between lower urinary creatinine excretion (UCr) and increased mortality, a finding presumed to reflect the effect of low muscle mass on clinical outcomes. Little is known about the relationship between UCr and other measures of body composition in terms of the ability to predict outcomes of interest.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using data from the Chronic Renal Insufficiency Cohort (CRIC), the relationship between UCr, fat free mass (FFM) as estimated by bioelectrical impedance analysis, and (in a subpopulation) whole-body dual-energy x-ray absorptiometry assessment of appendicular lean mass were characterized. The associations of UCr and FFM with mortality and ESRD were compared using Cox proportional hazards models.

RESULTS

A total of 3604 CRIC participants (91% of the full CRIC cohort) with both a baseline UCr and FFM measurement were included; of these, 232 had contemporaneous dual-energy x-ray absorptiometry measurements. Participants were recruited between July 2003 and March 2007. UCr and FFM were modestly correlated (rho=0.50; P<0.001), while FFM and appendicular lean mass were highly correlated (rho=0.91; P<0.001). Higher urinary urea nitrogen, black race, younger age, and lower serum cystatin C level were all significantly associated with higher UCr. Over a median (interquartile range) of 4.2 (3.1-5.0) years of follow-up, 336 (9.3%) participants died and 510 (14.2%) reached ESRD. Lower UCr was associated with death and ESRD even after adjustment for FFM (adjusted hazard ratio for death per 1 SD higher level of UCr, 0.63 [95% confidence interval, 0.56 to 0.72]; adjusted hazard ratio for ESRD per 1 SD higher level of UCr, 0.70 [95% confidence interval, 0.63 to 0.75]).

CONCLUSIONS

Among a cohort of individuals with CKD, lower UCr is associated with death and ESRD independent of FFM as assessed by bioelectrical impedance analysis.

Assessment of obesity in chronic kidney disease: what is the best measure?

PURPOSE OF REVIEW

Obesity is a major driver of the current epidemic of chronic kidney disease (CKD), but metrics of obesity in the CKD population have been studied sparsely. This review updates knowledge on this issue.

RECENT FINDINGS

Measures of abdominal obesity, waist circumference and waist-to-hip ratio (WHR), are better predictors than BMI of the high risk of mortality in predialysis and dialysis patients and waist circumference reliably reflects visceral fat in CKD patients. Skinfold thickness and WHR are superior to BMI for the classification of obesity in CKD patients. Multifrequency body impedance analysis (BIA) provides valid estimates of fat mass in hemodialysis patients.

SUMMARY

Skinfold thickness,WHR and multifrequency BIA are superior to BMI for measuring body fat in CKD patients and measures of abdominal obesity are stronger predictors of adverse clinical outcomes than the BMI. These metrics should be preferentially applied for the assessment of obesity in CKD, but it remains unproven that these techniques offer real advantages over the BMI in clinical practice in CKD patients.

Body adiposity index assess body fat with high accuracy in nondialyzed chronic kidney disease patients

OBJECTIVE

High body fat (BF) is an alarming condition that also affects nondialyzed chronic kidney disease (CKD) patients. Distinct methods are used to evaluate BF; however, in CKD population it remains unclear which one is more reliable showing high accuracy. Dual-energy X-ray absorptiometry (DXA), used as reference method to estimate adiposity, is expensive and time consuming to be applied in clinical settings. Recently, a new body adiposity index (BAI), that estimates BF from easily accessible measures, was validated in the general population. The aim of this study was to evaluate which simple and practical method, routinely used to estimate BF, shows the highest accuracy compared with DXA, in nondialyzed CKD patients.

DESIGN AND METHODS

In this cross-sectional study BF was estimated by DXA, bioelectrical impedance analysis (BIA), anthropometry (ANTHRO), and BAI. Serum leptin levels were determined.

RESULTS

Studied patients (n = 134) were 55% males, 54% overweight/obese, and 64.9 ± 12.5 years old, with estimated glomerular filtration rate (eGFR) = 29.0 ± 12.7 ml/min. The correlation coefficient was higher between DXA vs. ANTHRO (r = 0.76) and BAI (r = 0.61) than with BIA (r = 0.57), after adjusting for gender, age, and eGFR (P < 0.0001). Therefore, the Lin's concordance correlation coefficient and Bland-Altman plots were performed to measure the accuracy (C_b) between DXA with both ANTHRO and BAI. A higher accuracy (C_b = 0.82) and lower mean difference (-3.4%) was observed for BAI than for ANTHRO (C_b = 0.61; -8.4%). Leptin levels correlated (P < 0.0001) with DXA (r = 0.56) and BAI (r = 0.59).

CONCLUSIONS

These findings suggest that BAI estimates BF with high accuracy in nondialyzed CKD patients and may be helpful in the treatment of this population with increased BF.

Bioimpedância elétrica e sua aplicação em avaliação nutricional

A busca por métodos de estimativa da composição corporal é uma preocupação constante da comunidade científica, com vistas à obtenção de um acurado diagnóstico do estado nutricional de indivíduos e populações. A bioimpedância elétrica tem sido uma alternativa atraente na avaliação da composição corporal, pela possibilidade de se trabalhar com equipamento não invasivo, portátil, de fácil manuseio, boa reprodutibilidade e, portanto, viável para a prática clínica e para estudos epidemiológicos. Sua utilização, que tem como finalidade determinar o fracionamento da composição corporal, tem sido apontada como uma técnica capaz de superar alguns desafios encontrados em outros métodos para avaliar o estado nutricional. Entre os componentes da bioimpedância elétrica, o ângulo de fase consiste em uma ferramenta cada vez mais utilizada na prática clínica, sendo estudado como indicador prognóstico e de estado nutricional. Esse ângulo indica alterações na composição corporal e na função da membrana celular, portanto, no estado de saúde de indivíduos. Dada a carência de estudos brasileiros sobre determinadas aplicações da bioimpedância elétrica, a proposta deste estudo, buscando contribuir com a literatura, é traçar um panorama sobre o emprego dessa técnica e, ainda, apresentar trabalhos que a comparam com outros métodos de avaliação nutricional e composição corporal.