EAL

H/A: Body Composition Measurement (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the reproducibility of DXA measurements of body fat in HIV-positive patients representing a spectrum of severity of fat redistribution.

Inclusion Criteria:

HIV-positive subjects with and without lipodystrophy.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

Consecutive volunteers were enrolled from among HIV-positive subjects participating in two studies of HIV lipodystrophy at the Immunodeficiency Clinic at the Toronto General Hospital. One was a prospective study of previously antiretroviral-naive patients initiated on highly active antiretroviral therapy (HAART) containing a protease inhibitor. The other study was an ongoing double-blinded intervention trial in patients with established lipodystrophy as identified by a self-report questionnaire and an assessment by an experienced physician.

Design

Cross-sectional.

Statistical Analysis

Sample size of 30 was required to be able to estimate the coefficients of variation within ±15% with 95% confidence
Root mean square coefficients of variation were used to estimate minimum detectable differences for body fat content in different regions
Regional fat mass values were grouped and analyzed for the following anatomical regions: arms, legs, limbs (arms and legs), trunk, subtotal body (whole body excluding head) and whole body
Absolute minimum detectable difference was calculated by multiplying the minimum detectable difference by the mean fat mass value for each anatomical area.

Data Collection Summary:

Timing of Measurements

Subjects underwent same-day repeat whole-body DXA scans.

Dependent Variables

Body composition measured with whole-body DXA scans with the Hologic QDR 4500A Scanner.

Independent Variables

HIV infection
Presence of lipodystrophy.

Description of Actual Data Sample:

Initial N: 30 men

Attrition (final N): 30 men

Age: Mean age, 45.9 years (range, 32.5 years to 62.0 years)

Ethnicity: Not mentioned

Other relevant demographics: Mean BMI, 25.5 (range, 18.3 to 39.0)

Anthropometrics: Authors noted that age, weight, height and BMI were representative of the population

Location: Canada.

Summary of Results:

Variables	Coefficients of Variation Root Mean Square (RMS)-Coefficients of Variation (CV) (%)	Relative Minimum Detectable Difference *2.77RMS-CV (%)**	Absolute Minimum Detectable Difference MDD×Mean (g)
Head fat mass	2.5	7.0	72.7
Arm fat mass	4.0	11.0	159.8
Left arm fat mass	5.4	14.9	97.2
Right arm fat mass	6.2	17.2	121.4
Leg fat mass	3.1	8.5	312.7
Left leg fat mass	5.7	15.9	181.5
Right leg fat mass	4.1	11.4	142.2
Limb fat mass	2.6	7.3	375.7
Trunk fat mass	2.1	5.9	499.2
Subtotal fat mass	1.7	4.6	624.1

Other Findings

The root mean square coefficient of variation ranged from 4.0% for arm fat to 1.6% for total fat.

Relative and absolute minimum detectable difference values ranged from 11.0% or 160g for arm fat to 4.3% or 628g for total fat.

Author Conclusion:

In summary, this is the first study to report the reproducibility of DXA measurements of regional body fat mass in HIV-positive subjects. Minimal detectable differences were smaller than differences observed in some published cohorts and cross-sectional studies. This supports the use of DXA as a tool for evaluating the presence and severity of HIV lipodystrophy. The reported estimates of variability are useful in calculating sample size for studies using DXA as an endpoint and in determining whether longitudinal changes in DXA measurements are significant, in either observational or intervention trials. Finally, given the variability in DXA fat-mass values, longitudinal studies using DXA should endeavor to use paired analyses when reporting results.

Funding Source:

University/Hospital:

Toronto Hospital Immunodeficiency Clinic

Reviewer Comments:

The authors note that sex is known to affect body composition, and females exhibit different patterns of fat redistribution. Therefore, the values may not be generalizable to women being evaluated for HIV lipodystrophy.

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?		N/A
	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.)	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?	Yes
	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?	N/A
	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?	N/A
	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