H/A: Body Composition Measurement (2009)

Citation:
 
Study Design:
Class:
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Quality Rating:
Research Purpose:
  • To determine the validity of bioimpedance spectroscopy and anthropometric measurements to measure body composition in HIV-positive and HIV-negative women as compared with the values obtained with the reference stable isotope dilution method
  • To describe the body composition of HIV-positive lactating women in rural South Africa. 
Inclusion Criteria:
  • Delivery four to 20 weeks previously
  • Maternal age more than 15 years
  • Current breastfeeding of the infant
  • Arrival at clinic by 9:00 A.M. to allow sufficient time for the full range of measurements.
Exclusion Criteria:
  • Current acute illness that would influence hydration status (e.g., diarrhea or fever)
  • Admission to the hospital in the previous two weeks.
Description of Study Protocol:

Recruitment

The study was conducted in government health clinics in the field area of the Africa Centre for Health and Population Studies in a rural, northern part of KwaZulu Natal Province, South Africa. Mothers were identified for the study when they came to clinic for their infants' immunizations. Mothers were enrolled from November 2001 to April 2002.

Design

Cross-sectional study. 

Blinding Used 

HIV testing was anonymous; at the time of body composition measurement, HIV status was not known by subjects or study staff.

Statistical Analysis

  • For demographic and body-composition variables, differences between HIV-positive and HIV-negative mothers were tested for significance by using the chi-square test for categorical variables and the Student's T-test for continuous variables
  • Pearson product-moment correlations and paired T-tests were used to measure the bias, significance and degree of correlation between isotope dilution and bioimpedance spectroscopy measurements of total body water, fat-free mass and fat mass
  • Repeated-measures ANOVA was used to ascertain whether differences between groups and assessment methods were significant and whether the two-factor group times method interaction for all body composition variables was significant
  • Agreement between results of the two methods was evaluated by using the Bland-Altman model
  • Pearson product-moment correlations were used to determine the correlation between the isotope dilution measurement of fat-free mass and fat mass and anthropometric measurements.
Data Collection Summary:

Timing of Measurements

Total body water content of lactating mothers was measured 10 weeks after delivery. All measurements made on the day of enrollment.

Dependent Variables

  • Total body water content measured using bioimpedance spectroscopy and isotope dilution to measure fat-free mass and fat mass
  • Anthropometric measurements included height, weight, body mass index, mid-upper arm circumference and four skinfold thicknesses (triceps, biceps, subscapular and suprailiac)
  • Age-appropriate Durnin-Womersley equation for females was used to estimate body composition for all mothers from skinfold thicknesses.

Independent Variables

  • HIV infection measured with ELISA
  • CD4+ cell counts and total HIV RNA were also measured.  

 

Description of Actual Data Sample:
  • Initial N: 68 mothers were enrolled, 20 with HIV infection
  • Attrition (final N): Seven were excluded. Four were excluded due to implausible bioimpedance spectroscopy measurements, two were excluded due to incomplete isotope dilution procedures and one was removed as an outlier.
  • Age: Median age 24 years, range 15 to 40 years.

Other Relevant Demographics

  • None of the study participants had received antiretroviral drugs
  • Median viral load in HIV-positive mothers: 25,000 RNA copies per mL (range nondetectable, 170,000 copies per mL)
  • Median CD4+ cell count: 631 per mcL (range 179 to 1229 per mcL). 

Location

South Africa. 

 

Summary of Results:

 

Variables

HIV-positive Subjects (N=17) HIV-negative Subjects (N=44)

P-value

Height (cm)

159.8±4.5

158.2±5.3

0.275
Weight (kg) 66.8±9.2 62.9±11.9 0.228
BMI (kg/m2) 26.2±3.7 25.1±4.6 0.396
mid-upper arm circumference (cm) 29.6±3.5 28.4±3.9 0.301
Mid-upper arm muscle circumference (cm) 23.7±1.8 22.6±2.7 0.121
Triceps skinfold thickness (mm) 19.0±7.9 18.8±7.6 0.921
Biceps skinfold thickness (mm) 10.7±4.6 10.3±5.0 0.765
Subscapular skinfold thickness (mm) 22.3±7.4 19.2±6.2 0.116
Suprailiac skinfold thickness (mm) 22.2±9.9 20.5±8.2 0.502
Total body water - BIS (L) 31.2±3.0 29.2±3.9 0.056
Total body water - 2H20 (L) 29.5±3.1 27.7±3.4 0.072
Fat-free mass - BIS (kg) 41.7±4.2 38.8±5.2 0.045
Fat-free mass - 2H20 (kg) 40.2±4.3 37.8±4.7 0.072

Fat mass - BIS (kg)

25.2±6.8

23.9±7.9

0.542

Fat mass - 2H20 (kg) 26.6±7.6 25.1±8.7 0.532
Extracellular water - BIS (L) 14.2±1.4 13.7±1.8 0.318
Intracellular water - BIS (L) 17.1±2.2 15.5±2.3 0.020

Other Findings

Total body water, fat-free mass and fat mass measurements determined by bioimpedance spectroscopy were correlated with isotope dilution measurements in HIV-positive (R=0.664, 0.621 and 0.872, respectively,  P<0.01) and HIV-negative (R=0.876, 0.868 and 0.932, respectively, P<0.001) mothers.

Total body water measured by bioimpedance spectroscopy was greater than that measured by the isotope dilution method in both HIV-positive (1.8L) and HIV-negative (1.5L) women.

Fat mass or fat-free mass did not differ significantly by method.

BMI, mid-upper arm circumference and all skinfold-thickness measurements correlated strongly (R>0.62, P<0.001) with fat mass measured by isotope dilution in both groups.

BMI and mid-upper arm circumference correlated (R>0.64, P<0.001) with fat-free mass in HIV-negative mothers but not in HIV-positive mothers. 

Author Conclusion:

In summary, we have shown that bioimpedance spectroscopy provides an estimate of body composition that is 105% to 106% of the estimate obtained with the isotope dilution method, as measured under our study conditions. This is a reasonable approximation of the values obtained with the reference method, and given our study conditions, we are not sure which method provides the truest estimation. Regardless of the true value, the relation does not vary for HIV-positive and HIV-negative mothers. Bioimpedance spectroscopy is a simple field technique that is useful for assessing body composition and for comparing groups of HIV-positive and HIV-negative women in this location. Breastfeeding mothers living in our study area appear to be adequately nourished in terms of body composition and anthropometry. Studies of women with advanced HIV disease are needed to more fully test the limits of the bioimpedance spectroscopy method for accurate assessment of body composition.

Funding Source:
Government: Mid-career grant no. 1 K24 AI/HDO1671-01 from NIAID/NIH
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:
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) N/A
  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) N/A
 
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? Yes
  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? Yes
3. Were study groups comparable? Yes
  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.) Yes
  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? Yes
  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.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  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? Yes
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  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? Yes
  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? Yes
  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? Yes
  7.7. Were the measurements conducted consistently across groups? N/A
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  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)? Yes
  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? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
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