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H/A: Body Composition Measurement (2009)

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

The main objectives of this study were:

  • To assess the effect of HIV on energy balance
  • To examine the relationship of parameters of immunodeficiency to energy balance
  • To examine the interrelationship of different components of energy balance in asymptomatic HIV sero-positive men.
Inclusion Criteria:

Cases

  • Asymptomatic HIV seropositive men (CD4 count four to 482x106 per liter)
  • Seropositive for HIV through ELISA and confirmatory immunoassay. 

Controls

HIV seronegative men.
Exclusion Criteria:
  • AIDS diagnosis
  • Weight loss greater than 5% usual body weight in last year
  • Diarrhea, bowels open more than three times daily for more than two weeks
  • More than three episodes of fever or night sweats in past year
  • History of intravenous drug use
  • Coexistent chronic systemic disease
  • Use of anabolic agents or megestrol
  • Women, due to differences in body composition.
Description of Study Protocol:

Recruitment

  • HIV-seropositive men recruited consecutively from HIV Outpatients Department at Chelsea and Westminster Hospital between May 1993 and September 1994
  • Controls recruited from patients attending the genitourinary clinics, associates of HIV-seropositive patients and clinic staff.

Design

Case-control study.

Intervention

Not applicable, due to energy balance measurements.

Statistical Analysis

  • HIV-seropositive subjects, grouped according to peripheral CD4 cell count using cutoffs of 100x, 200x and 300x106 per liter
  • ANCOVA used to compare the mean values between cases and controls
  • F-statistic was used to test whether the value of the parameter under study was different in at least one group. When statistical differences were found, a multiple comparisons test was performed with Bonferroni corrections.
  • ANCOVA also performed to compare HIV-seronegative with seropositive
  • Linear regression was used to derive equation relating REE with fat-free mass.
Data Collection Summary:

Timing of Measurements

  • Components of energy balance examined in HIV seropositive and seronegative men and compared
  • Blood analysis performed on day of REE measurements
  • Urine sample collected within five days of REE measurement
  • Food diaries completed within two weeks of REE measurement.

Dependent Variables

  • Height and weight
  • Energy and protein intake measured using five-day food diaries
  • Small bowel absorption and permeability assessed using four sugar probes
  • Resting energy expenditure calculated using indirect calorimetry
  • Nitrogen loss estimated from 24-hour urine collection
  • Body composition measured using four-site anthropometry, DEXA, tetrapolar bioelectrical impedance and 24-hour urine creatinine 
  • Blood samples analyzed for thyroxine, thyroid stimulating hormone, C-reactive protein, fasting triglycerides, serum albumin and peripheral blood CD4 lymphocyte subset count.

Independent Variables

HIV seropositive or HIV seronegative.

Control Variables

  • Age
  • Antiretroviral treatment.
Description of Actual Data Sample:
  • Initial N: 104 HIV seropositive men and 57 HIV seronegative controls
  • Attrition (final N): 104 seropositive men, 57 controls
  • Mean age
    • Seropositive men: 37.9±8.2 years
    • Controls: 31.3±7.3 years.
  • Ethnicity: Not mentioned 
  • Anthropometrics: Controls were supposed to be age-matched; however, age differed between seropositive and seronegative subjects (P<0.0001)
  • Location: United Kingdom.
Summary of Results:

 

HIV+ (N=104)

 HIV- (N=57)

P-Value
Mean Age (Years) 37.9±8.2 31.3±7.3  <0.00001

BMI

22.4

23.4

0.06

Energy Intake (kcal/d)

2243

1908

0.05
Protein Intake (g/d) 82.8 76.5 0.32
Nitrogen Intake (g/d) 13.2 12.2 0.32
24-Hour Urine Nitrogen (g/d) 12.7 14.4 0.27
REE/FFM (kcal/kg/d) 32.7 30.7 <0.0001
RQ 0.84 0.84 0.91
CHO Oxidation (g/kg FFM/d) 3.9 3.7 0.64
Fat Oxidation (g/kg FFM/d) 1.6 1.8 0.14
Protein Oxidation (g/kg FFM/d) 1.4 1.6 0.16
Lactulose Probe 0.4 0.3 0.007
L-rhamnose Probe 9.3 11.3 0.01
Lactulose/Rhamnose Ratio 0.05 0.03 <0.0001
D-Xylose 30.2 32.9 0.14
3-O-Methyl-D-Dlucose 43.9 51.6 0.003
D-Xylose/3-O-Methyl-D-Glucose Ratio 0.70 0.65 0.07
Fat-Free Mass (kg) 56.8 54.5 0.05
Fat Mass (kg) 12.6 16.1 0.001
Proportion Fat (%) 17.6 22.0 <0.0001
Appendicular Muscle Mass (kg) 25.2 24.9 0.60
Bone Mineral Content (kg) 3.0 3.0 0.72

Other Findings

  • HIV-seropositive individuals had similar mean values irrespective of CD4 count for most parameters
  • Resting energy expenditure per kg of fat-free mass was raised (P<0.0001), fat mass was decreased (P=0.001), fat-free mass was increased (P=0.05), energy intake was higher (P=0.05), absorption of L-rhamnose (P=0.01) and 3-O-methyl-D-glucose was decreased (P=0.003) and small bowel permeability was increased (P<0.0001) in HIV-seropositive men, compared with HIV-seronegative controls
  • HIV-seropositive subjects with a CD4 count less than 100x106 per liter had decreased absorption of L-rhamnose (P<0.05), D-xylose (P<0.05) and 3-O-methyl-D-glucose (P<0.05), compared with HIV-seropositive subjects, at higher CD4 counts and had a similar resting energy expenditure to HIV-seronegative controls
  • Protein intake, carbohydrate, fat and protein oxidation, 24-hour nitrogen excretion and appendicular muscle mass were similar in HIV-seropositive men and controls.
Author Conclusion:

HIV infection exerts a direct effect on parameters of energy balance that varies with the severity of immunosuppression.

Funding Source:
Reviewer Comments:
  • Measurements taken over two-week period
  • Controls not age-matched
  • Authors note that 24-hour urine creatinine is an unsuitable outpatient measure of FFM in this population.
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? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? ???
  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? 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.) ???
  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? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? Yes
  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? Yes
  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? 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? 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? ???
  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? ???
  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)? 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