Perit Dial Int
29(Supplement_2):
78-82
2009
© 2009 International Society for Peritoneal Dialysis
Part 3: Clinical Experiences |
IS SUBJECTIVE GLOBAL ASSESSMENT A GOOD INDEX OF NUTRITION IN PERITONEAL DIALYSIS PATIENTS WITH GASTROINTESTINAL SYMPTOMS?
Yanjun Li,
Jie Dong and
Li Zuo
Renal Division, Department of Medicine, Peking University First Hospital;
Institute of Nephrology, Peking University; and Key Laboratory of Renal
Disease, Ministry of Health of China, Beijing, PR China
Correspondence to: J. Dong, Renal Division, Peking University First Hospital,
8 Xishiku Street, Xicheng District, Beijing 100034 PR China.
dongjie{at}medmail.com.cn
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ABSTRACT
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Objective: We investigated whether patients with
gastrointestinal (GI) symptoms were prone to be diagnosed as malnourished by
subjective global assessment (SGA) by simultaneously evaluating SGA and other
indices of nutrition in a cross-sectional survey of peritoneal dialysis (PD)
patients.
Patients and Method: From June 2006 to June 2007, 214
PD patients were involved in the study. We recorded results of a GI symptoms
questionnaire (GSQ) and SGA. Other indices of nutrition included dietary
intake, chemistry examination, anthropometry, handgrip strength, and lean body
mass measured by creatinine kinetics.
Results: Mean age of the 214 PD patients enrolled in
the study was 60.22 ± 14.02 years, and mean dialysis duration was 60.22
± 14.02 months. Of the 214 patients, 56 (27.16%) were diagnosed as
malnourished by SGA. The mean GSQ scores were 9.37 ± 1.71 (range: 8
– 17). There were 90 patients with GSQ scores of 8 (group 1), 80
patients with scores of 9 or 10 (group 2), 44 patients with scores of 11 or
more (group 3). The prevalence of malnutrition diagnosed by SGA was
significantly different in the three groups: 15.56% in group 1, 27.5% in group
2, and 45.45% in group 3 (p = 0.02). However, we observed no
difference between the three groups in mid-arm circumference, skinfold
thickness (biceps, triceps, subscapular, and suprailiac), daily protein and
energy intake, handgrip strength, lean body mass, and serum albumin and
prealbumin levels (p > 0.05).
Conclusions: Our results showed that the reliability of
SGA in PD patients with GI symptoms remains worth exploring. These patients
are possibly diagnosed as malnourished by SGA, although many other indices of
nutrition are not necessarily bad.
KEY WORDS: Nutrition; subjective global assessment; gastrointestinal symptoms.
Subjective global assessment (SGA) is a simple and convenient method for
evaluating nutrition based on medical history and physical examination
(1). It has been successfully
applied in predicting complications and mortality in end-stage renal disease
(ESRD), including in hemodialysis and peritoneal dialysis (PD) patients
(2,3).
However, SGA was found not to be a reliable predictor of degree of
malnutrition as compared with the "gold standard"
method—that is, total body nitrogen
(4). Some unknown complications
and nutrition-related factors may affect the validity of SGA. The U.S.
National Kidney Foundation therefore recommended that general indices of
nutrition, but not a single index should be applied to evaluate nutrition
status. At the same time, they encouraged exploration of the validity of SGA
in populations with specific illnesses
(5).
Gastrointestinal (GI) symptoms are a common phenomenon in ESRD patients,
with a prevalence ranging from 32% to 79% in dialysis patients
(6–8).
Uremic toxins, metabolic acidosis, inadequate dialysis, deficient gastric
emptying, drug side effects, psychosocial factors, and a history of GI disease
were correlated with GI symptoms in ESRD patients. In SGA, GI symptoms and
related changes in dietary intake are two main factors that contribute to the
final SGA score. It is hypothesized that PD patients may tend to be diagnosed
as malnourished by SGA when they have GI symptoms.
The aim of our study was to understand whether patients with GI symptoms
are prone to be diagnosed as malnourished by SGA by simultaneously evaluating
SGA and other indices of nutrition in a cross-sectional survey of PD patients.
To our knowledge, this is the first study to explore the validity of SGA in PD
patients with various degrees of GI symptoms.
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PATIENTS AND METHODS
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This was a cross-sectional study. From June 2006 to June 2007, 214 PD
patients who gave informed consent were included. All patients agreed to
simultaneously complete two questionnaires and indices of nutrition when they
came to visit their doctors and dietitian. The response rate for the
questionnaires was 100%. All the patients were dialyzed using lactate-buffered
glucose PD solutions and the twin-bag connection system (Baxter Healthcare,
Guangzhou, China). All patients received three or four 2-L exchanges
daily.
GASTROINTESTINAL SYMPTOMS QUESTIONNAIRE
To assess the severity of GI symptoms, we used the self-administered GI
symptoms questionnaire (GSQ). With a development procedure similar to that of
the GI symptoms rating scale (GSRS), the GSQ contains items selected on the
basis of clinical experience and reports in the literature concerning the GI
symptoms of dialysis patients
(6–9).
All 8 items were rated in 5 steps relating to intensity and effects on daily
living, as shown in Table 1.
The GSQ data are presented as total scores. The higher the score, the more
pronounced the symptoms. All patients self-completed the GSQ based on the
month preceding the assessment.
SUBJECTIVE GLOBAL ASSESSMENT
The definition of malnutrition was based on the original version of the SGA
scores (1). Patients scored as
"A" were defined as well-nourished; "B," as mildly
malnourished, and "C," as severely malnourished. The SGA is based
on medical history and physical examination, which is divided into 5 parts:
weight change, dietary intake change, GI symptoms that have persisted for more
than 2 weeks, functional impairment, and physical examination (loss of
subcutaneous fat, muscle wasting, edema). The SGA was performed by an
experienced dietitian who was blinded to all clinical and biochemical
variables of the patients.
CLINICAL VARIABLES AND NUTRITION
The demographic data collected included age, sex, body mass index (BMI),
diabetes mellitus (DM) status, and dialysis duration. All patients completed
3-day dietary records before they visited the dietitian. The daily protein and
energy intakes (DPI and DEI) were calculated using a software program (PD
Information Management System: Peritoneal Dialysis Center, Peking University,
Beijing, China). The total calorie intakes included intakes from both diet and
dialysate. The DPI and DEI were both normalized for standard body weight.
Collections of 24-hour dialysate and urine were performed to calculate fluid
removal and solute clearances. Weekly urea clearance (Kt/V) and total
creatinine clearance (CCr) were calculated using standard methods. The
distribution volume of urea (V), which is generally assumed to be equal to
total body water, was calculated using the Watson equation. Biochemical
indices (serum albumin, prealbumin, hemoglobin, urea nitrogen, creatinine)
were analyzed using a Hitachi chemistry analyzer. Lean body mass (LBM) was
measured by the creatinine kinetics method according to the formula
recommended by Blake (10).
Anthropometric measurements were taken in millimeters by one trained dietitian
using standard skinfold calipers. Measurements included mid-arm circumference
(MAC) and biceps, triceps, subscapular, and suprailiac skinfold thickness
(SFT). For each site, the observer obtained three readings, the average value
of which was used for further calculations. Handgrip strength (HGS) was
evaluated in both the dominant and non-dominant arm using a dynamometer. The
test was repeated three times, and the greatest value was recorded in
Newtons.
STATISTICAL ANALYSES
Statistical analysis was performed using the SPSS software (version 11.0:
SPSS, Chicago, IL, U.S.A.). Continuous variables are expressed as mean
± standard deviation, and categorical variables, as percentages.
One-way ANOVA was used to compare the differences between groups. The
chi-square and nonparametric statistical tests were used where appropriate. A
value of p < 0.05 indicates statistical significance.
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RESULTS
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A total of 214 PD patients (106 men, 108 women) were enrolled in the study,
with ages ranging from 15 to 83 years (mean: 60.22 ± 14.02 years). Of
the 214 patients, 80 (37.38%) had DM. The mean duration of follow-up on PD was
21.5 ± 18.7 months. The mean BMI was 23.58 ±
3.79kg/m2; urea nitrogen, 20.87 ± 6.23 mmol/L; creatinine,
838.94 ± 307.41 µmol/L; weekly Kt/V, 1.88 ± 0.57; and weekly
total CCr, 61.6 ± 26.74 L/1.73 m2. Of the 214 patients, 56
(27.16%) were diagnosed as malnourished by SGA.
The mean GSQ scores were 9.37 ± 1.71 (range: 8 – 17). Of the
214 patients, 124 (57.94%) had GI symptoms. There were 90 patients with GSQ
scores of 8 (group 1), meaning no GI symptoms; 80 patients with scores of 9 or
10 (group 2), meaning at least 1 positive item; and 44 patients with scores of
11 or more (group 3), meaning more than 1 positive item. There were no
differences of age, sex, or dialysis duration between the three groups, but
the prevalence of DM was significantly different: 26.67% in group 1, 43.75% in
group 2, and 47.72% in group 3 (p = 0.02). The prevalence of
malnutrition diagnosed by SGA was also significantly different: 15.56% in
group 1, 27.5% in group 2, and 45.45% in group 3 (p = 0.02,
Figure 1). However, we observed
no difference in MAC, SFT-biceps, SFT-triceps, SFT-subscapular,
SFT-suprailiac, DPI, DEI, HGS, LBM, and serum albumin and prealbumin levels
between the three groups (p > 0.05,
Table 2). Only DPI levels were
faintly different between the groups (p = 0.06).
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Figure 1 — The prevalence of malnutrition in the three groups of patients as
diagnosed by subjective global assessment (p = 0.02).
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View this table:
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TABLE 2 Nutritional
Variablesa in
Three Peritoneal Dialysis Groups with Different Degrees of Gastrointestinal
Symptoms
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DISCUSSION
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Assessments of nutrition in dialysis patients are imperative, although the
task is not necessarily easy. The purpose of such assessments is obviously the
identification of patients at risk for complications and a poor outcome before
such complications have developed. The SGA is an inexpensive, simple, and
convenient method of measuring nutrition status, and it is recommended by the
U.S. National Kidney Foundation clinical practice guidelines as a regular tool
to use in large populations of patients
(5). However, the SGA has been
shown to have some shortcomings in evaluating nutrition.
First, there has been controversy about correlations between SGA and serum
albumin
(11–14),
which suggested that the link between SGA and important markers of
inflammation and prognosis is not very strong. This inconsistency raised
questions about the validity of SGA
(15). Second, both our
previous work and a study by Gurrenbun et al. revealed an overlap of
anthropometry and biochemical indices of nutrition with the normal and
abnormal SGA groups, suggesting that SGA misclassifies a large number of
subjects
(16,17).
Third, when compared with the "gold standard" method—that
is, total body nitrogen—the sensitivity and specificity of SGA to
predict a patient with malnutrition were only approximately 50% – 70%.
Cooper et al. (4)
therefore thought that SGA is suitable only to differentiate severely
malnourished patients. Their presumption was that comorbid illnesses and
nutritional factors may contribute to the final SGA score. For example, GI
symptoms originating from inadequate dialysis, infection, or acute comorbidity
may have a significant effect on SGA score without adversely affecting
nutrition status. As GI symptoms and dietary intake—two key parts of the
SGA score—change, they will inevitably contribute to the SGA score,
because the final score will be B or C only if more than half the items in the
SGA are rated B or C.
Our cross-sectional study revealed that 57.93% of patients have varying
degrees of GI symptoms, and 27.16% of patients were diagnosed as malnourished
by SGA. Patients with DM were prone to GI symptoms. As we hypothesized before
the study, patients with GI symptoms had a higher prevalence of SGA scores
showing malnutrition. However, other indices of nutrition reflecting visceral
and somatic protein storage and anthropometric variables in patients with GI
symptoms were not significantly different from those in patients without GI
symptoms. These results suggest that we should carefully consider the
reliability of SGA in patients with GI symptoms. Combining SGA with other
indices of nutrition may be especially important in this population.
Two other points also need to be discussed. One is about selection of the
SGA version. In the literature on chronic kidney disease, at least 5 different
SGA tools have been reported, almost none of which have been tested in a large
validation (15). Only Cooper
et al. compared the original SGA version to the "gold
standard" method (4),
revealing that SGA is not a good tool to differentiate malnutrition. Our idea
for the present study came from Cooper's report, which is why we used the
original SGA version used by Cooper. The second point concerns how to evaluate
GI symptoms in dialysis patients. Although the GSRS is a rating scale for
measuring GI symptoms, it was originally established for patients with
irritable bowel syndrome and peptic ulcer disease
(18); later it was applied in
gastroesophageal reflux disease (GERD)
(19). The questions in the
GSRS—that is, the frequently seen symptoms—are not necessarily
suitable to dialysis patients, because the pathogenesis of GI symptoms may be
different in dialysis patients
(7,9).
For example, epigastric pain is more frequently seen in patients with peptic
ulcer disease and GERD, but less in PD patients
(20). We therefore developed a
self-administered GSQ containing selection items drawn from clinical
experience and reports in the literature on the GI symptoms of dialysis
patients
(6–9).
In our practice, the GSQ had shown its simplicity and convenience. More
clinical research is needed to verify its validity in diagnosis and evaluation
of treatment.
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CONCLUSIONS
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Our single-center cross-sectional study showed that the reliability of SGA
in PD patients with GI symptoms is still worth exploring. Patients are
diagnosed to possibly be malnourished by SGA although their scores on many
other indices of nutrition are not necessarily bad.
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ACKNOWLEDGMENTS
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The authors express their appreciation to the patients and staff of the
peritoneal dialysis center at First Hospital, Peking University, for their
participation in the study. This study was funded by National "211
project" Peking University EBM group (38-18). Author Dong Jie
contributed to design and oversaw the whole study and the drafting of the
paper. Author Zuo Li contributed to the drafting of the paper.
This study was the basis of an oral presentation at the 2008 International
Society for Peritoneal Dialysis conference in Istanbul, Turkey.
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ABSTRACT
PATIENTS AND METHODS
