CKD: Measuring Body Composition (2009)

Citation:

Sanches MR, Avesani CM, Kamimura MA, Lemaos MM, Axelsson J, Vasselai P, Draibe SA, Cuppari L. Waist circumference and visceral fat in CKD: A cross-sectional study. Am J Kidney Dis. 2008; 52: 66-73.

PubMed ID: 18440683
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To evaluate the association between waist circumference (WC) and visceral fat in a cohort of patients in which CKD not yet on dialysis therapy, and also to test whether the association of WC with some CVD risk factors was similar to that found for visceral fat.

Inclusion Criteria:

Adult patients with CKD not on dialysis therapy.

Exclusion Criteria:
  • Active malignancy
  • Human immunodeficiency virus seropositivitiy
  • Viral hepatitis
  • Autoimmune and rheumatoid disease
  • Severe dyslipidemia
  • Ascites
  • Use of steroids, statins, fibrates or immunosuppressives.
Description of Study Protocol:

Recruitment

Patients were recruited from a controlled prospective study of the impact of rosuvastatin on the progression of coronary artery calcification.

Design

Cross-sectional study, done on the same day patients were assessed for nutritional status and anthropometrics. After seven days of enrollment, fasting blood collection, dual-energy X-ray absorptiometry (DXA) and abdominal CT were performed.

Statistical Analysis

  • Student unpaired T-test
  • Mann Whitney U test
  • Chi-Square
  • Person linear correlation coefficients
  • Data are expressed as mean±SD for normally distributed variables and median and range for skewed variables
  • Differences with P less than 0.05 were considered statistically significant.

 

Data Collection Summary:

Timing of Measurements

One-time measurement.

On the same day, enrolled patients were assessed for nutritional status and anthropometrics. Within seven days of enrollment, patients also underwent fasting blood collection, dual-energy X-ray absorptiometry (DXA) and abdominal CT.

Dependent Variables

  • Waist circumference (cm
  • Triceps skinfold (mm)
  • BMI (kg/m2)
  • Body weight (kg)
  • Subjective global assessment
  • HDL-C
  • LDL-C
  • Triacylglicerol
  • HOMA index.

Independent Variables

  • Visceral fat using CT
  • Subcutaneous fat using CT
  • Total body fat (kg) using DXA [DPX scanner (Lunar Radiation Corp., Madison, WI)].

Control Variables

Sex.

 

Description of Actual Data Sample:
  • Initial N: 122 (75 males, 47 females)
  • Attrition (final N): 122 (75 males, 47 females)
  • Age: Mean 55.3 years (range 27 to 79 years)
  • Other relevant demographics: The majority of patients were in stage 3 or 4 CKD. 35% of  patients had a history of CVD.
  • Anthropometrics: BMI was greater for the subset of patients with higher WC (equal or more than 93.3cm). 60% of women and 59% of men were overweight. 51% of the patients had  higher WC. Almost all patients were well nourished.
  • Location: Sao Paulo, Brazil. 
Summary of Results:

Body Composition and Anthropometrics

Variables

Men

Women

P

Weight (kg)

71.6±11.8 66.8±16.2 0.08

BMI (kg/m2)

26.4±3.9

28.1±6.5 

0.1 

Waist circumference (cm)

94.5±10.3

93.8±14.9 

0.8 

Triceps skinfold (mm) 13±5.4  23±8.8  <0.01 
Total-body fat by skinfold (kg) 18.1±6.2 25.4±10.1  <0.01 

DXA

Total-body fat (kg)

 

17.3±6.9

 

24.7±10.8 

 

<0.01 

Lean body fat (kg) 51.4±5.5 35.3±5.2  <0.01 
Truncal fat (kg) 11.4±4.5 13.4±6.1 0.07 

Abdominal fat by CT*

Abdominal fat area (cm2)

 

254 (53.3 to 594)

 

251.1 (44.8 to 1,017.9) 

 

0.6 

Visceral fat area (cm2) 93.5 (2.4 to 332.6) 48.1 (1.1 to 592.2)  <0.01 
Subcutaneous fat area (cm2) 135.6 (37 to 367.7) 196.3 (19.5 to 506.6)  <0.01 

*Values expressed in median (range).

Correlation Coefficients for Visceral and Subcutaneous Fat with Anthropomorphic Measures and DXA in 122 Patients With Chronic Kidney Disease

 

Log

Visceral Fat

Log

Subcutaneous Fat

Men

Anthropometrics Method

 

 

 

 
Weight (kg) 0.61 0.73
BMI (kg/m2) 0.68 0.80
Waist circumference (cm) 0.75 0.81
Triceps skinfold (mm) 0.51 0.68
Total-body fat by skinfold (kg) 0.65 0.82

DXA

Total-body fat (kg)

 

 

0.75

 

 

0.84

Truncal fat (kg) 0.79 0.80

Women

Anthropometrics method

 

 

 

 

 

 

Weight (kg) 0.63 0.70
BMI (kg/m2) 0.76 0.78
Waist circumference (cm) 0.81 0.78
Triceps skinfold (mm) 0.68 0.66
Total-body fat by skinfold (kg) 0.73 0.76

DXA

Total-body fat (kg)

 

 

0.78

 

 

0.74

Truncal fat (kg) 0.84 0.77

 All P values were less than 0.01.

  • WC was significantly correlated with visceral fat in both men and women (R=0.75, R=0.81; P<0.01), respectively
  • WC was also significantly correlated with subcutaneous fat in both men and women (R=0.81, R=0.78; P<0.01), respectively
  • 77% of patiens with greater WC had greater visceral fat when they were split according to median values of WC fat (93.3cm) and visceral fat (84.7cm2); k statistic was 0.56, indicating relatively good agreement between methods
  •  BMI showed a lower correlation coefficient (R=0.68 men and R=0.76 woment) with visceral fat, and 69% of patients with greater BMI (median, 26.5kg/m2) had greater visceral fat; k statistic was 0.36 (poor agreement) compared to visceral fat. 

Other Findings

Correlation Cefficient for Markers of CVD Risk

  Waist Circumference P

Log

Visceral Fat

P

Log

Subcutaneous

Fat

P

Men

HDL-C (mg per dL)

 

 

-0.43

 

 

<0.01

 

 

-0.41

 

 

<0.01

 

 

-0.41

 

 

<0.01

Log triacylglicerol (mg per dL)

 

0.37

<0.01 0.25 <0.05 0.35 <0.01
Log HOMA index 0.51 <0.01 0.51 <0.01 0.47 <0.01

In women, WC correlated with age (R=0.45; P<0.01); C-reactive protein (R=0.58; P<0.01) and Homa index (R=0.40; P<0.01), whereas visceral fat correlated to  triacylglicerol (R=0.39; P<0.01) and LDL-C (R=0.36; P<0.05).

 

Author Conclusion:

Waist circumference was strongly associated with visceral fat in patients with CKD. Associations found between WC and some CVD risk factors were similar to those observed for visceral fat, particularly in men. These findings suggest that waist circumference may be a simple and inexpensive tool to be used more often in epidemiological studies involving patients with CKD.

Funding Source:
Government: Fundacao de Amparao a Pesquisa do Estado de Sao Paulo (FAPESP); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)
Not-for-profit
Oswaldo Ramos Foundation
Other non-profit:
Reviewer Comments:
  • Most of the study results focused on correlation coefficient between tests. Correlation coefficient is inadequate for comparing a new method with an established one.
  • Kappa statistics were used to compared waist circumference fat by CT or BMI by anthropometric measurements to visceral fat by DXA. Median values of WC fat or BMI and visceral fat were used to classified patients into 2x2 tables kappa statistics calculation. This is data-driven and has little clinical value.
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? Yes
  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? Yes
  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) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? N/A
  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")? No
4. Was method of handling withdrawals described? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  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? ???
  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? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? N/A
  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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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? Yes
  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? Yes
  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? Yes
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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  8.6. Was clinical significance as well as statistical significance reported? No
  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