EAL

H/A: Body Composition Measurement (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate the degree to which lean body mass and fat free mass assessed by DXA, bioelectrical impedance analysis and skinfold thickness measurements correlates with total body potassium in men and women with AIDS wasting
To investigate the bias between commonly available techniques, including DXA, bioelectrical impedance analysis and skinfold thickness measurements in the determination of fat free mass in men and women with AIDS wasting.

Inclusion Criteria:

AIDS wasting (weight less than 90% of ideal body weight, or weight loss more than 10% of original, or both)
Subjects were ambulatory and were screened for participation in treatment studies of AIDS wasting
None had received anabolic agents, including growth hormone, testosterone and megestrol acetate within three months of the study.

Exclusion Criteria:

Subjects with severe diarrhea, recent opportunistic infection, a change in antiretroviral medication within the previous six weeks or a creatinine concentration more than 133µmol per L
Women receiving any form of hormone replacement therapy or who had a positive pregnancy test result.

Description of Study Protocol:

Recruitment

Subjects were evaluated at the General Clinical Research Center of the Massachusetts General Hospital between 1995 and 1998.

Design

Cross-sectional study.

Statistical Analysis

Estimates of fat-free mass by DXA, bioelectrical impedance analysis and skinfold thickness measurements were compared with those from total body potassium among HIV-infected men and women by univariate analyses
Fat mass and fat-free mass determined by DXA, bioelectrical impedance analysis and skinfold thickness measurements were compared by paired T-test and regression analysis, with separate analyses in the men and women
Bias was calculated as the mean of the difference between two techniques ± standard deviation.

Data Collection Summary:

Timing of Measurements

Comparisons between measurements were made.

Dependent Variables

Total body potassium determined in a whole body counter with sodium iodide detectors fixed above and below the patient at the xiphoid process
Fat-free mass determined through DXA, bioelectrical impedance analysis and skinfold thickness measurements at three sites (subscapular, biceps, triceps and suprailiac)
Comparisons made using different bioelectrical impedance analysis equations.

Independent Variables

AIDS wasting.

Description of Actual Data Sample:

Initial N: 132 patients, 63 men and 69 women
Attrition (final N): 132 patients
Age: Mean age, men: 41.6±8.1 years, women: 36.0±5.5 years
Other relevant demographics: None of the subjects exhibited clinical lipodystrophy.

Anthropometrics

Mean CD4 count: Men, 185±215 cells per mm³; women, 360±285 cells per mm³
Mean viral load: Men, 185,424±257,260 copies per ml; women, 53,563±68,292 copies per ml
Protease inhibitor use: Men, 19%; women, 28%.

Location

Massachusetts.

Summary of Results:

Variables	Men	Women
DXA	R=0.79, P<0.0001	R=0.84, P<0.0001
BIA, RJL	R=0.69, P<0.0001	R=0.49, P=0.007
BIA, Lukaski et al	R=0.69, P<0.0001	R=0.71, P<0.0001
BIA, Lukaski and Bolonchuk	R=0.69, P<0.0001	R=0.70, P<0.0001
BIA, Kotler et al	R=0.62, P<0.0001	R=0.58, P<0.001
BIA, Deurenberg et al	R=0.68, P<0.0001	R=0.46, P=0.011
BIA, Segal et al	R=0.71, P<0.0001	R=0.48, P=0.009
BIA, Van Loan and Mayclin	R=0.60, P<0.0001	R=0.44, P=0.016
BIA, Gray et al	R=0.70, P<0.0001	R=0.54, P=0.002
SKF	R=0.75, P<0.0001	R=0.41, P=0.026

Other Findings

BMI was comparable, but percentage body fat, as measured by DXA, was higher in women than men (28.0±8.1% compared with 16.4±7.3%, P<0.0001).

Lean body mass determined by DXA was highly correlated with total body potassium in men (R=0.79, P<0.0001) and women (R=0.84, P<0.0001).

Fat-free mass determined by bioelectrical impedance analysis and DXA were significantly different (P<0.01 in men and P<0.0001 in women).

The difference between fat-free mass determined by DXA and bioelectrical impedance analysis was significantly greater with greater weight and body fat, particularly in HIV-infected women (R=-0.39, P=0.001 for weight; R=-0.60, P<0.0001 for fat).

The comparability of fat-free mass and fat mass determined by DXA and bioelectrical impedance analysis was dependent on the specific bioelectrical impedance analysis equation used.

Among men, no single bioelectrical impedance analysis equation was more highly predictive of fat mass and fat-free mass in comparison with DXA.

Author Conclusion:

The differences between DXA, bioelectrical impedance analysis and skinfold thickness measurements in the determination of fat mass and fat-free mass are significant in patients with AIDS wasting. Bioelectrical impedance analysis overestimates fat-free mass compared with DXA in those with greater body fat. Standard bioelectrical impedance analysis equations may not accurately estimate fat free mass and fat mass in men and women with AIDS wasting.

Funding Source:

Government:

NIH grants R01-DK49302, M01-RR01066, F32-DK09218

Industry:

Reviewer Comments:

Large number of subjects.

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?	Yes
	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.)	Yes
	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?	Yes
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)?	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?		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