|Year : 2014 | Volume
| Issue : 2 | Page : 70-75
Assessment of Nutritional Status by Dual-Energy X-Ray Absorptiometry in Chronic Kidney Disease Patients without Dialysis
Yan Yan, Niansong Wang, Guihua Jian, Xiaoguang Zhang, Xiaoxia Wang, Qin Xue, Xuping Gao
Department of Nephrology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University, Shanghai - 200 233, China
|Date of Web Publication||27-Oct-2014|
Department of Nephrology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University, Shanghai - 200 233
Source of Support: The research is supported by grant 81270824 from the Project of National Nature Science Foundation of China, Shanghai Science and Technology Project (11DZ1921904; 11410708500), Conflict of Interest: None
Objective: The objective was to evaluate the assessment of nutritional status by dual-energy X-ray absorptiometry (DEXA) in chronic kidney disease (CKD) patients not receiving dialysis. Patients and Methods: A total of 143 patients in stage 4-5 without receiving dialysis were enrolled and classified into well-nourished and malnourished groups by subjective global assessment. Biochemical and anthropometric measurements were performed. Simultaneously, body composition including lean body mass (LBM) and fat mass (FM) was evaluated by DEXA. Results: Compared with well-nourished patients, malnourished patients showed lower pre-albumin (ALB) levels, but higher C-reactive protein (CRP) levels. There was no significant difference in serum ALB between both groups. For either men or women, body weight, body mass index, and glomerular filtration rate (GFR) were lower in the malnourished group. For the men, triceps skin-fold thickness (TSFT), mid-arm circumference (AC), mid-arm muscle circumference (AMC), LBM-DEXA and FM-DEXA were significantly lower in the malnourished patients. For the women, TSFT, mid-AC and FM-DEXA, but mid-AMC and LBM-DEX, were not significantly lower in the malnourished patients. There was a significant correlation between LBM-DEXA and mid-AMC. A significant correlation also existed between FM-DEXA and TSFT. Multiple logistic regressions showed that low percentage of FM, high serum CRP level and low GFR were independent risk factors for malnutrition. Conclusions: Low percentage of FM, high serum CRP and low GFR are independent risk factors for malnutrition. Estimation of LBM and FM by dual X-ray absorptiometry is in consistent with traditional anthropometric measurements. It's noteworthy that DEXA, a reliable and easy-to-perform assessment method, can sensitively detect early malnutrition and may be useful in monitoring nutrition changes in CKD patients.
Keywords: Absorptiometry, chronic kidney disease, malnutrition dual-energy X-ray
|How to cite this article:|
Yan Y, Wang N, Jian G, Zhang X, Wang X, Xue Q, Gao X. Assessment of Nutritional Status by Dual-Energy X-Ray Absorptiometry in Chronic Kidney Disease Patients without Dialysis. J Integr Nephrol Androl 2014;1:70-5
|How to cite this URL:|
Yan Y, Wang N, Jian G, Zhang X, Wang X, Xue Q, Gao X. Assessment of Nutritional Status by Dual-Energy X-Ray Absorptiometry in Chronic Kidney Disease Patients without Dialysis. J Integr Nephrol Androl [serial online] 2014 [cited 2019 May 21];1:70-5. Available from: http://www.journal-ina.com/text.asp?2014/1/2/70/143387
| Introduction|| |
Currently, the mortality of patients suffering from end-stage renal disease (ESRD) is increasingly high. ,, Malnutrition is one of the most important risk factors for ESRD. Previous reports have demonstrated that the incidence of malnutrition in ESRD patients was 20-50%, frequently resulting in hypo-immunity, infections and elevated mortality. ,, Accordingly, it is advisable that treatments of potential malnutrition in chronic kidney disease (CKD) patients may effectively reduce mortality. At present, approaches used to assess nutritional status include anthropometric, biochemical, subjective global assessment (SGA), and bioelectrical impedance method. However, all these methods have their disadvantages. Dual-energy X-ray Absorptiometry (DEXA) is used as a method to assess clinical nutritional status.  It calculates body composition according to the reduction of different organizations on X-ray extent from stable dual-energy photon beam. Furthermore, the accuracy of DEXA could hardly be influenced by edema frequently observed in CKD patients. Theoretically, DEXA could provide sufficient information of protein and calorie intake, and thus could be considered as a convincing and nontraumatic assessment. In this article, the fat mass (FM) and lean body mass (LBM) of 143 CKD patients in stage 4-5 without receiving dialysis were assessed by using DEXA to evaluate the nutritional characters of ESRD patients and the clinical values of DEXA in assessing the nutritional status of CKD patients.
| Patients and methods|| |
One hundred and forty-three CKD patients aged >30 and <75 in stage 4-5 without receiving dialysis, who visited the outpatient department or were hospitalized in our hospital from July 2004 to February 2008 were enrolled. The Ethics Committee of The Sixth People ' s Hospital Affiliated to Shanghai Jiao Tong University approved the study. The diagnosis and staging of CKD were based on the CKD staging criteria embodied in Kidney Disease Outcomes Quality Initiative developed by National Kidney Foundation.  Glomerular filtration rate (GFR) was calculated by Cockcroft-Gault formula. Exclusion criteria were as follows: Complicated acute or chronic infections during the past 3 months; administration of immunosuppressant or immunopotentiator; complicated hepatic or severe cardiac diseases; active hemorrhage; other complicated chronic consumptive diseases (e.g., tuberculosis, cancer).
One hundred and forty-three CKD patients were enrolled who met the inclusion criteria and gave informed consent. And SGA was made based on the evaluation of weight loss, subcutaneous fat, muscle consumption and other two assessments. Each assessment was divided into three grades: A: Good nutrition; B: Mild to moderate malnutrition; C: Severe malnutrition. Based on the results of above assessments and criteria described in Detsky reference, they were divided into 1 = well-nourished; 2 = mild to moderate malnutrition; 3 = severe malnutrition. Detailed methods were the same as those described in documents.  Finally, 143 CKD patients were divided into malnourished (SGA: Grade B-C) and good malnourished (SGA: Grade A) groups.
All patients abstained from food for peripheral venous blood sampling and blood serum separation. Biochemical, creatinine (Cr), albumin (ALB), pre-ALB, C-reactive protein (CRP), total cholesterol (TC), triglyceride (TG) and tissue factor (TF) were determined by autoimmune analyzer manufactured by Roche Diagnostics Elecsys type 2010. HB was determined by CD300 hematology analyzer.
Body height was determined by body height and sitting height scale; body weight was determined in fasting, after defecation and urination with single-underwear; body mass index (BMI, BMI = [body weight]/[body height] 2 kg/m 2 ) and relative body weight (RBW, RBW = [actual weight]/[ideal body weight] × 100%) were calculated. Triceps skin-fold thickness (TSFT) and upper arm circumference (AC) were determined by tape and skin-fold instrument according to standardized methods. And mid-arm muscle circumference (AMC) was also calculated (AMC, AMC = AC-3.14 × TSFT).
Fat mass and lean body mass assays
General bone mineral density and body composition were determined by dual-energy X-ray analyzer Prodigy type manufactured by American Lunar Company. These two assays could accurately demonstrate general bone mineral density, net weight, and the content of fat, muscle and bone in each part. In addition, LBM, FM, bone mineral content and related parameters could be analyzed and calculated by Lunar software version 3.4 (Lunar Corp., USA).
Statistical analysis was performed using SPSS 11.5 software (IBM Corporation, USA) package. Two-side P < 0.05 was considered to be statistically significant. Measurement data were presented as x- + s while enumeration data were as presented as %. Inter-group variability was calculated by nonpaired t-test or Mann-Whitney U-test. Enumeration data were evaluated by accurate Chi-square test. Correlation between variables was evaluated by linear regression and Spearman rank correlation analysis. Scatterplot was used to evaluate the correlation between dual X-ray absorptiometry (DXA) and anthropometry. Independent correlation test was also performed on multiple variables and malnutrition by logistic multiple regression.
| Results|| |
The average age of these enrolled patients was 61.9 ± 10.9 (36-75) years old, and 79 cases were male (61.3 ± 12.1 years old) and the other 64 cases were female (62.2 ± 11.2 years old); BMI: 21.7 ± 5.8 kg/m 2 ; Cr clearance: 19.1 ± 10.2 ml/min (11.2-28.9 ml/min). The primary diseases included 57 cases of primary glomerular disease, accounting for 39.9%; 56 cases of diabetic nephropathy, accounting for 39.1%; 20 cases of hypertensive renal disease, accounting for 14.0%; 4 cases of gouty nephropathy, accounting for 2.8%; 4 cases of polycystic kidney disease, accounting for 2.8%; 2 cases of unknown causes, accounting for 1.4%. There were 62 cases in malnourished group (accounting for 43.3%), while 81 cases in well-nourished group (accounting for 56.7%). There were 34 males and 28 females in the malnourished group; and 58 cases were patients of moderate malnutrition (SGA: Grade B), and 4 cases of severe malnutrition (SGA: Grade C). There were 45 males and 36 females in the well-nourished group.
Inter-group comparison of nutritional parameters
In comparison to well-nourished patients, malnourished patients displayed decreased Body weight and BMI, elder in age, reduced GFR (P < 0.001), and anthropometric parameters such as AMC, AC and TSFT, and decreased LBM and FM evaluated by DEXA. However, there were no significant differences in serum ALB, hemoglobin, blood urea nitrogen and TF levels between well-nourished and malnourished patients. The patients in the malnourished group displayed a significant decrease in pre-ALB level (P < 0.05) and an increase in CRP level (P < 0.01) [Table 1].
|Table 1: Inter-group comparison of nutritional parameters between well-nourished and malnourished CKD patient groups|
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Comparison of nutritional parameters between chronic kidney disease patients of different genders
Male patients in malnourished group displayed significant decreases in anthropometric parameters, LBM, FM, GFR, and Cr values; and female patients in malnourished group displayed a decrease in anthropometric parameters, TSFT and AC values without statistically significant difference in AMC, decreased FM and GFR without statistically significant differences in LBM and Cr levels [Table 2]. There was no gender difference in TC, high-density lipoprotein (HDL) or TG levels observed in this research. Male patients in malnourished group displayed increased HDL and cholesterol levels, but other lipid parameters remained similar. The lipid spectrum between female patients of malnourished and well-nourished groups was similar.
|Table 2: Comparison of nutritional parameters between CKD patients of different genders|
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Dual X-ray absorptiometry assessments for chronic kidney disease patients and their correlation with other different nutritional parameters
As presented in [Figure 1]a, there was a strong correlation between LBM determined by DEXA assay and AMC as one of anthropometric parameters (r = 0.864, P < 0.001, n = 143).
|Figure 1: The correlation between dual-energy X-ray absorptiometry (DEXA)- lean body mass and arm muscle circumference (a), between DEXA-fat mass and triceps skin-fold thickness (b)|
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As presented in [Figure 1]b, there was a strong correlation between FM determined by DEXA assay and TSFT as one of anthropometric parameters (r = 0.799, P < 0.001, n = 143).
Factor analysis on the risk of malnutrition
Malnutrition being a dependent variable, single factor analysis on 143 cases of CKD patients suggested that: Low FM percent, high CRP level, low GFR, low LBM percent and pre-ALB were all risk factors for malnutrition in CKD patients (P < 0.05). Furthermore, Logistic regression analysis also suggested: Low DEXA-FM percent, high serum CRP level, and low GFR were independent risk factors for malnutrition in CKD patients (P < 0.05). However, there was no statistically significant difference between serum pre-ALB and DEXA-LBM percentage [Table 3]. The Logistic regression formula was P/(1-P) = EXP (−0.69-3.24 × 1 + 3.06 × 2-0.87 × 3), in which X1 represented DEXA-FM percentage, and X2 represented CRP level, and X3 represented GFR.
|Table 3: Logistic regression analysis on the risk factors of malnutrition for CKD patients|
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| Discussion|| |
Chronic kidney disease patients in various stages may develop malnutrition of various degrees, which manifests itself as reduced body weight, BMI, abnormal anthropometric parameters, and serum ALB loss, etc. , Of all enrolled 143 CKD patients in stage 4-5 in this research, 43.5% patients developed malnutrition, which was consistent with previous findings. ,
The mechanism of DEXA is explained by the transverse propagation of two photons of different energy through one specific site of body, and the energy of original photon may attenuate with an index mode. However, the attenuating extent varies in different organisms of different density. Thus, the content of organism could be calculated by recording the different attenuating extent by the organism on the energy of two photons. This approach is convenient, nontraumatic and reproducible. The previous researches , demonstrated that the accuracy of FM and LBM determination was 1-1.5%, and this result was rarely influenced by pathological changes of body fluid content or chemical composition.
Well-nourished and malnourished groups were well classified by SGA method. The absolute values of LBM and FM of all patients were determined by DEXA, and related percentages were also calculated. The results showed that there was a statistically significant difference in LBM between well-nourished and malnourished male patients (P < 0.01). However, no such difference in LBM was observed in female patients. It is thus reasonable to propose that female patients have higher FM and lower LBM percentages in comparison to those of male patients, and FM reduction seems to be more significant than LBM consumption in the early stages of malnutrition.
Furthermore, both in male and female patients, there were statistically significant difference in FM values between well-nourished and malnourished groups (P < 0.05). Logistic regression analysis indicated that low lipid content percentage was an independent risk factor for malnutrition, which was consistent with previous reports.  In addition, Heimbürger et al. suggested that the determination of FM percentage by DEXA could not only assess the nutritional status of CKD patients accurately, but also could reflect body nutritional changes more sensitively than traditional LBM. Moreover, it may be valuable to diagnose potential malnutrition in its early stages and worthy of clinical expansion.
Correlations between FM values and TSFT, LBM values and AMC were observed. Although direct anthropometry has been more extensively used as it is simple and easily measurable, it may provide distorted information of CKD patients due to changes in tissue water content. Thus, it may fail to reflect the nutritional changes of patients timely and properly.  The standardized requirement of skin-fold method to assess body FM is high, and large assessing errors may be caused by different individuals, as well as different manipulations. We herein assigned an experienced physician to assess anthropometric parameters according to unified criteria, and correlations were observed between final results and data collected by DEXA. However, this condition is difficult to achieve in clinical practice.
Malnutrition has been recognized as an independent risk factor to predict mortality in hemodialysis patients. Recent studies have shown that chronic inflammation, which is frequently noted in CKD patients, is a main cause of malnutrition, cardiovascular and atherosclerotic diseases. , Inflammation may give rise to protein malnutrition, and play an important role in atherosclerosis simultaneously. The complex interactions between these three are called malnutrition-inflammation-atherosclerosis syndrome.  In the present study, the patients were classified as well-nourished and malnourished groups, assessed by SGA. Compared with well-nourished patients, malnourished patients showed higher CRP levels and a higher proportion of CRP elevation. Multiple logistic regression demonstrated that after adjusting for age and GFR level, CRP remained an independent risk factor for malnutrition.
It is worth noting that there was no difference in serum ALB levels between malnourished and well-nourished patients, and serum ALB level was not related to LBM assessed by the DEXA. We speculate that it may be in part due to relatively higher proportion of diabetic nephropathy in the present cohort. More urine protein loss will cause that serum ALB level cannot reflect the real nutritional status. Nevertheless, negative correlations were found between serum ALB level and inflammatory response (assessed by CRP level). Stenvinkel et al. held that inflammation by up-regulating proteolysis and by increasing anorexia would be expected to exacerbate hypoalbuminemia.
To sum up, malnutrition was frequently observed in CKD patients in stage 4-5. Low DXA-FM percentage, high serum CRP level and low GFR value are highly valuable to predict malnutrition. Inflammatory status is possibly related to malnutrition and hypoalbuminemia. There was a good correlation between FM, LBM and traditional anthropometric parameters. In addition, the assessment of nutritional state by DEXA-FM percentage in CKD patients is accurate and reproducible. Thus, malnutrition of CKD patients could be diagnosed in early stages, and this method has fairly high clinical value.
| Acknowledgments|| |
The research is supported by grant 81270824 from the Project of National Nature Science Foundation of China, Shanghai Science and Technology Project (11DZ1921904; 11410708500). The funders had no role in study design, data collection and analysis, decision to publish and preparation of the manuscript.
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[Table 1], [Table 2], [Table 3]