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CKD: Measuring Body Composition (2009)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To assess the prevalence of malnutrition in a cohort of patients with CRF before the start of dialysis treatment and evaluate and compare markers of nutritional status in patients, including hand-grip muscle strength (HGS), estimates of lean body mass (LBM) by means of dual-energy x-ray absorptiometry (DXA), anthropometric measurements (AMs) and creatinine kinetics (CK), and such biochemical markers as serum levels of albumin, transthyretin (TTR) and retinol-binding protein (RBP). 

Inclusion Criteria:
  • Terminal CRF starting dialysis treatment
  • Shortly (average 10 days) after the start of dialysis
  • Healthy subjects recruited for comparative studies of HGS.
Exclusion Criteria:
  • Older than 70 years old
  • Unwillingness to participate in the study
  • Acute renal failure caused by severe systemic disease such as  vasculitis. 
Description of Study Protocol:

Recruitment

  • Patients were recruited from a prospective cohort study of arteriosclerosis and lipid metabolism in patients initiating dialysis therapy 
  • Healthy volunteers were recruited for comparative studies of HGS (controls).

Design

Cross-sectional study. 

Statistical Analysis 

  • Mann-Whitney U test and student's unpaired T-test were used to compare differences between control subjects and patients with CKD
  • Linear regression analysis (R) and Spearman rank correlation test (Rho)
  • Bland-Altman plots for LBM and FM
  • Logistic regression
  • Multiple regression analysis, HGS was normalized to the percentage of the values of healthy controls of the same sex, and percentages of FM and LBM were normalized by the average values in both men and women
  • All results were given as mean+SD. Two-tailed P less than 0.05 was considered statistically different.

 

Data Collection Summary:

Timing of Measurements

One-time measurement. 

Dependent Variables

  • Body weight (kg)
  • BMI
  • LBM was measured by different methods: DXA (kg), AMs (cm) and CK (kg). DXA was performed using the DPX-L machine (Lunar Corp., Madison, WI) and data were evaluated using Lunar software version 3.4. AMs, including midarm muscle circumference (MAMC) and measurements of triceps, biceps, subscapular, and suprailiac skinfold thickness. CK was calculated from the urinary creatinine using Keshaviah et al calculations.
  •  Fat mass (FM) was measured by DXA and AMs
  •  Hand-grip muscle strength (HGS) was evaluated in both arms; for patients with an arteriovenous fistula in the non-dominant arm, the measurement was performed in the dominant arm. All measurements  were repeated three times, with the greatest value recorded
  • SGA classifications: Well nourished (SGA,1), mild (SGA, 2), moderate (SGA,3), severe malnutrition (SGA, 4)
  • TTR (mg per dL)
  • Albumin (g per L)
  • RBP (mg per dL)
  • Vitamin A (umol per L)
  • CRP (mg per L).

Independent Variables

Nutrition status. 

Control Variables

  • Creatinine
  • Hydration status
  • Protein restriction.

 

Description of Actual Data Sample:

Initial N

  • 115 (69 males, 46 females)
  • Controls: 69 (33 males, 36 females).

Attrition (Final N)

  • 115 (69 males, 46 females)
  • Controls: 69 (33 males, 36 females).

Age

  • Mean age: 52 years old; range from 23 to 69 years
  • Healthy controls: Mean age, 43.6±9 years.

Ethnicity

White, Asian and African.

Other relevant demographics

The majority of patients were white (96%). Controls were ten years younger than CKD patients. The cause of CKD was diabetic nephropathy (27%); chronic glomerulonephritis (26%); polycystic kidney disease (15%); and other causes or unknown (32%). Patients were under a low-protein diet (0.6g per kg per day). Antihypertensives were prescribed, such as angiotensin-converting enzyme inhibitors, calcium channel blockers and others. Creatinine clearance was 9±3ml per minute (range, 2.0 to 21.0ml per minute).

Anthropometrics

BMI and weight were statistically different between the well-nourished and malnourished patients, regardless of gender. Mean BMI was 24.4 to 4.5kg/m2 (range, 14.3 to 38.7kg/m2).

Location

Stockholm, Sweden.

Summary of Results:

 

Test Comparisons

 
Population
N Pair
Linear Regression Analysis
Bland-Altman Limit of Agreement (LOA) Analysis
Slope (R)
What is X Axis? (Units)
What is Y Axis? (Units)
Intercept
Mean Bias
Lower LOA (Lower CI)
Upper LOA (Upper CI)
Standard Deviation (SD)
LBM by DXA and anthropometry measure (AM)
CKD close to pre-dialysis treatment or shortly after dialysis treatment
115
0.893
DXA (kg)
AM (kg)
~23
~2
~ -8
 
 
 
 
~ 10
    
LMB by DXA and CK
CKD close to pre-dialysis treatment or shortly after dialysis treatment
115
0.632
DXA (kg)
CK
 (kg)
 
~20
~9
~ -10
 
~9
 
LBM by AM and CK
CKD close to pre-dialysis treatment or shortly after dialysis treatment
115
0.616
AM
 (kg)
CK
(kg)
~20
~8
~ -10
 
~26
 
FM by DXA and AM
CKD close to pre-dialysis treatment or shortly after dialysis treatment
115
0.887
DXA (kg)
AM
(kg)
~8
~ -3
 
~ -8
 
~8
 

 Other Findings

  • 48% of the patients had malnutrition (SGA, 2 to 4)
  • Hand-grip muscle strength (HGS) was markedly less among the patients than healthy controls in both men (38±12 vs. 56±10kg; P<0.0001) and women (24+7 vs. 36±7kg; P<0.0001)
  • HGS correlated with LMB estimated by means of DXA (R=0.70; P<0.0001), CK (R=0.70; P<0.0001), and AMs (R=0.664; P<0.0001). Finally, CrCl correlated with HGS in women (R=0.42; P=0.0008), but not men
  • Creatinine clearance did not correlate with MAMC or LBM estimated by means of AMs or DXA, whereas significant correlations were found between CrCl and LBM CK in both men (R=0.67; P0.0001) and women (R=0.54; P=0.0003)
  • MAMC correlated with HGS (R=0.44; P<0.0001) but this correlation was only significant among men (R=0.39; P=0.002)
  • Serum albumin level was not related to HGS or LBM
  • Low HGS (X2=13.4; P=0.0003), low percentage of FM DXA (X2=12.4; P=0.0004), high serum CRP levels (X2=5.1; P=0.02), and female sex (X2=3.5; P=0.06) were independent factors associated with malnutrition, whereas serum albumin level and percentage of LBM DXA did not attain statistical significance
  • LBM estimated by means of AMs, DXA or CK; FM estimated by means of AMs and DXA;  HGS; and CrCl were less among malnourished patients regardless of sex.

 

Author Conclusion:

The present study shows a high prevalence of malnutrition in pre-dialysis patients with CRF and suggests that HGS is a reliable, inexpensive and easy-to-perform nutritional parameter in patients with CRF. Conversely, serum albumin level seems to be a poor nutritional marker in patients with advanced CRF.

Funding Source:
Government: Swedish medical research council
Industry:
Baxter extramural grant program; Hospal
Pharmaceutical/Dietary Supplement Company:
Commodity Group:
Not-for-profit
Martin Rinds Foundation
Other non-profit:
Reviewer Comments:
  • The hand-grip muscle strength was compared with other methods as a nutritional marker for CKD patients, using correlation coefficient, which can only show relationship between the methods. Bland-Altman plots showed the best agreement between anthropometric methods and DXA in measuring lean body mass.
  • Most of the results were based on correlation coefficients, which does not provide information on any clinical value
  • Controls  were selected from a different population for comparative studies of HGS. Patients were selected from a previous prospective cohort study
  • Bland-Altman Limit of Agreement (LOA) Analysis data only reported in figures. Values extracted were estimated from the figures.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? No
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? No
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? No
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) No
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? ???
4. Was method of handling withdrawals described? ???
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? No
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? No
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.7. Were the measurements conducted consistently across groups? No
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.2. Were correct statistical tests used and assumptions of test not violated? No
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes