- Open Access
A simple protein-energy wasting score for survival prediction of maintenance hemodialysis patients
© The Author(s) 2015
- Received: 10 July 2015
- Accepted: 19 September 2015
- Published: 17 December 2015
The nutritional status of patients on maintenance hemodialysis (MHD) is a strong predictor of their survival. We assessed the reliability of a protein-energy wasting (PEW) score as a predictor of the survival of Japanese MHD patients.
The study subjects were 254 MHD patients. PEW score was from 0 (worst; group 1) to 4 (best; group 4) and was derived from four body nutrition compartments: serum albumin, body mass index, a normalized serum creatinine value, and protein intake. The main outcome was all-cause mortality.
A total of 26 patients died during the follow-up period of 36 months. The Kaplan-Meier analysis revealed that the group whose score was 0–1 had a significant lower survival rate than the groups with higher (2–4) PEW scores (P < 0.0001). In multivariate analysis, hazard ratios (HRs) were 0.214 (confidence interval (CI) 0.068–0.610, P < 0.005) between group 1 and group 4, 0.176 (0.054–0.510, P < 0.005) between group 2 and group 4, and 0.249 (CI 0.054–0.857) between group 3 and group 4.
A new simple PEW score predicts the survival of MHD patients and may help to better identify subgroups of MHD patients with a high mortality rate.
- Protein-energy wasting
- All-cause mortality
The mortality rate of maintenance hemodialysis (MHD) patients is still higher than the mortality rate of overall general population of Japan as a whole . Since protein-energy wasting (PEW) is a strong predictors of MHD patient mortality [2–4], evaluation of their nutritional status is essential to optimally manage MHD patients.
Many different mechanisms, including muscle wasting, abnormalities of gastrointestinal, hematopoietic, and immune systems, and abnormal activation of the inflammatory process, have been reported to explain the link between PEW and mortality in HD patients [5, 6]. Clinical assessment of the nutritional status of MHD patients is mandatory, but since there is no single gold-standard marker, easily measured in a reproducible manner that is unaffected by confounding conditions , MHD patients must be screened for PEW by various measures on a regular clinical practice [8, 9].
The aim of this study was to evaluate a simple PEW score, based on various clinical and biological values, as a predictor for mortality of MHD patients.
Subjects and protocol
This was a retrospective cohort study conducted at a single center in Japan. The subjects were recruited from among patients who had been routinely dialyzed via an arteriovenous fistula in the dialysis unit of the Shinjuku Ishikawa Clinic for at least 6 months by the procedure . The Institutional Review Board of the Shinjuku Ishikawa Clinic approved all study protocols (I-02-2015), and they were performed in accordance with the Declaration of Helsinki guidelines regarding ethical principles for medical research involving human subjects. Informed consent was obtained from every subject.
MHD patients with malignancy, active inflammation, liver cirrhosis, gastrointestinal bleeding, or severe illness were excluded from participation as subjects. The patients who were enrolled as subjects (n = 254) had been undergoing stable regular HD with a bicarbonate dialysate. The underlying disease was chronic glomerulonephritis in 95 cases, diabetic nephropathy in 74 cases, hypertensive nephrosclerosis in 52 cases, polycystic kidney disease in 18 cases, chronic pyeonephritis in 9 cases, and in 6 cases, the underlying disease was unknown.
All patients were on thrice-weekly HD therapy. Blood pressure (BP) was measured with a mercury sphygmomanometer with the patient in the supine position after resting for 10 to 15 min, and mean values for the 1-month period preceding enrollment were used in the statistical analysis. Dry weight was targeted to achieve a normotensive edema-free state. Information regarding previous cardiovascular disease and smoking status was collected from the patient’s medical records. Diabetes was defined as a presence of diabetes and/or a fasting plasma glucose concentration >126 mg/dl or HbA1c value >6.5 % or prescription of glucose-lowering agent.
Laboratory and nutritional parameters
Blood was sampled before dialysis session after an overnight fast. Serum urea nitrogen, creatinine, albumin, and C-reactive protein (CRP) levels were measured with an autoanalyzer (Hitachi Co., Tokyo, Japan) by standard laboratory methods. Body mass index (BMI) was calculated by dividing body weight in kilograms by the square of their height in meters and was expressed in kilogram per square meter. Urea kinetics were assessed by measuring a blood-based dialysis parameter, Kt/V , and the mean value of the three measurements during each of the 3 months before the start of the study was used in the analysis.
Definition of protein-energy wasting score
Serum albumin (g/dL)
Body mass index (kg/m2)
Data for endpoints were obtained from hospital charts. The primary endpoint of the study was all-cause mortality during the follow-up period from January 1, 2011 to December 31, 2014. The vital status of the subjects was determined by searching the electronic dialysis records. Patients were censored if they were alive on December 31, 2014.
Normally distributed, unpaired continuous values were expressed as means ± SD and compared by performing an analysis of variance. Nonparametric values were expressed as median values and compared by performing the Kruskal-Wallis test. Categorical values were expressed as percentages and compared by performing the Fisher’s exact test. We considered some variables whose P value was <0.10 according to the results of the univariate logistic regression analyses, in addition to gender, presence of diabetes and history of myocardial infarction, peripheral vascular disease and stroke, CRP, and Kt/V.
The survival analysis was based on the Kaplan-Meier curve with subjects censored for death. A log-rank test was used to compare the survival rates of two groups. A multivariate Cox proportional hazard model with adjustment for multivariate factors was used to evaluate mortality risk. Results were expressed as a hazard ratio (HR) with 95 % confidence interval (CI). A P value <0.05 was considered to be statistically significant. All statistical analyses were performed by using the SAS version 9.2 software program (SAS Institute Inc., Cary, NC, USA) for Windows personal computers.
Baseline characteristics of the study subjects according to the PEW score
Clinical and laboratory parameters
Normal nutritional status
Number of patients
Number of deaths
59.3 ± 12.8
66.2 ± 11.5**
63.1 ± 11.8**
55.9 ± 12.6
53.6 ± 11.3
Dry weight (kg)
60.2 ± 13.5
56.2 ± 9.6**
56.8 ± 14.0**
60.4 ± 13.2**
70.7 ± 10.2
1.65 ± 0.20
1.59 ± 0.17**
1.59 ± 0.21**
1.65 ± 0.20**
1.78 ± 0.16
Dialysis vintage (years)
11.0 ± 7.7
8.8 ± 7.7
11.0 ± 6.9
12.0 ± 8.1
10.3 ± 7.8
C-reactive protein (mg/dL)
0.29 ± 0.41
0.31 ± 0.29
0.31 ± 0.43
0.26 ± 0.31
0.33 ± 0.63
Serum albumin (g/dL)
3.88 ± 0.32
3.60 ± 0.28**
3.76 ± 0.29**
3.98 ± 0.27**
4.13 ± 0.19
1050 ± 217
808 ± 185**
999 ± 178**
1120 ± 173*
1208 ± 200
641 ± 121
507 ± 101**
632 ± 110*
684 ± 108
678 ± 99
1.45 ± 0.24
1.39 ± 0.23
1.47 ± 0.24*
1.49 ± 0.24*
1.38 ± 0.19
nPCR (g protein/kg/day)
0.93 ± 0.17
0.78 ± 0.14**
0.88 ± 0.16**
1.00 ± 0.16
1.01 ± 0.13
Survival predictive factors by Cox proportional hazard models
Patients characteristics and PEW score
Peripheral vascular disease
Score 2 versus 0–1
Score 3 versus 0–1
Score 4 versus 0–1
The HR was 0.239 (CI 0.088–0.607, P < 0.005) between the severe wasting group (score 0–1; group 1) and the normal nutritional status group (score 4; group 4), 0.131 (0.041–0.361, P < 0.001) between the moderate wasting group (score 2; group 2) and the normal nutritional status group (group 4) and 0.207 (CI 0.047–0.664) between slight wasting group (score 3; group 3) and the normal nutritional status group (score 4; group 4) (data not shown). In multivariate analysis, HRs were respectively 0.214 (CI 0.068–0.610, P < 0.005) between group 1 and group 4, 0.176 (0.054–0.510, P < 0.005) between group 2 and group 4, and 0.249 (CI 0.054–0.857) between group 3 and group 4 (Table 3).
We evaluated a simple PEW score based on simple available clinical parameters and demonstrated that it can predict survival of MHD patients. Although an abnormal nutritional status is frequently reported in MHD patients, there is no single nutrition parameter that can predict PEW [15–17]. We hope to take advantage of a simple nutritional marker to make recommendations and improve the outcomes of MHD patients.
Hypoalbuminemia is a strong predictor of mortality in MHD patients. Kalantar-Zadeh et al.  showed that a serum albumin levels <3.8 g/dL in MHD patients were correlated with increased cardiovascular deaths independent of demographic, clinical, or laboratory characteristics, and Malfra et al.  demonstrated that a serum albumin level <3.7 g/dL was a strong predictor for mortality of dialysis patients. A 10-year cohort study reported an increased risk of death in HD patients with serum albumin level below 3.8 g/dL . However, Friedman and Fadem  have recently shown that serum albumin levels should be used cautiously as a nutritional marker in patients with chronic kidney disease (CKD) because low serum albumin levels in HD patients are known to be associated with both malnutrition and inflammation.
A lower prevalence of inflammation has been reported in dialysis patients in Asian countries, including Japan and Korea, and the lower prevalence may depend on genetic factors and cultural habits, including diet intake [22, 23]. Baseline obesity in MHD patients appears to be paradoxically associated with a higher survival rate [24, 25]. Asian-Americans have been reported to have a much lower adjusted relative mortality rate than Caucasian dialysis patients, but Asian-Americans have a significantly lower BMI . The International Society of Renal Nutrition and Metabolism (ISRNM) proposed a BMI of less than 23 as a diagnostic criterion for PEW in patients with chronic kidney disease (CKD), but they have not expanded their recommendation to South Asian CKD patients .
nPCR is associated with dietary protein intake , and nPCR has been reported to be an independent predictor of mortality in MHD patients . A study by Chandna et al. showed a substantial drop in the nPCR in CKD patients in the 3 months preceding the start of dialysis . The K/DOQI clinical practice guidelines recommended a daily protein intake of 1.2–1.3 g/kg/day for MHD patients and contributed to the low nPCR levels . Lukowsky et al. found that a decrease in nPCR of over 0.2 g/kg/day within a 3-month period was associated with increased risk of death .
Because no single parameter provides a comprehensive and conclusive assessment of nutritional status, a collective evaluation of multiple nutritional markers is recommended by K/DOQI guidelines . A recent panel of experts suggested using markers from four different categories (biochemistry, body mass, muscle mass, and dietary intake) for the clinical diagnosis of PEW . Three out of those four categories should be selected but at least one biochemical indicator must be included. However, to the best our knowledge, their combination has not yet been tested for assessing nutritional status in HD patients.
Moreau et al.  developed a simple PEW score including one parameter from each major group generally identified to interfere in nutritional status: (1) biological parameters, (2) body composition, (3) muscle mass, and (4) nutrient intake. It seems important to add laboratory information, such as serum levels of albumin and Cr to other clinical information, such as BMI . Since muscle mass, which is the major part of the body strongly associated with survival, is difficult to assess, they chose to use predialysis Scr values normalized by BSA. The Scr/BSA reflects the difference in Western and Asian and may differ by Cr intake and metabolism. This may be the reason why Cr is not used routinely. Indeed, SCr/BSA gave a better fit in the Cox model than raw Scr . Finally, they added information on nutrient intake by entering in the score the protein intake as estimated by normalized protein nitrogen appearance (nPNA also called nPCR). This value belongs to all current international recommendations and can be calculated easily by using dialysis generator software. Added to the model, it improved survival prediction over albumin alone.
It should be noted that the score by itself was not better than the four parameters added into the model as separate variables . That was not unexpected because information given by the score is already brought by all variables included into the score. However, we believe that this is the interest of this score to encourage the dialysis staff to pay attention to all these variables taken together. The PEW score could be obtained within minutes at bedside, with no additional equipment, at no expense and therefore be added to the arsenal of patient’s general record and follow-up. The final patient classification we obtained corresponds well to the published literature on the prevalence of nutritional disorders in dialysis patients: 37 % of patients present with moderate and 19 % with severe impairment in their nutritional status .
The routine use of the simple nutritional score may help to identify PEW in MHD patients. Further studies may be needed to verify the robustness of the PEW score in Asian populations because of the differences in body composition and clinical practice.
The authors are very grateful to the medical staff of Shinjuku Ishikawa Clinic who provided high-quality data. This study was in part supported by a grant from the Japan Promotion Society for Cardiovascular Disease.
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