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H/A: Caloric Needs (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To investigate whether resting energy expenditure is elevated in early asymptomatic HIV-infected females and to study the contribution of a cytokine (tumor necrosis factor-alpha) to hypermetabolism.
Inclusion Criteria:
Cases were HIV-infected, controls were not
Exclusion Criteria:
  • Subjects with fever
  • Impaired kidney function
  • Known endocrinological disease
  • History of opportunistic infections or malignancy
  • Subjects with current or prior usage of one or a variety of medications including retroviral medications or other immune modulators, anabolic steroids and antidepressant drugs known to affect metabolism.
Description of Study Protocol:
  • Recruitment: Methods not described
  • Design: Case-control study.

Statistical Analysis

  • ANOVA and ANCOVA used to assess differences in descriptive characteristics, REE and substrate utilization
  • Pearson correlations were performed to study the correlation of TNF-alpha and the CD4 count with REE
  • Regression analysis was used to examine the correlation between TNF-alpha and the CD4 cell count.
Data Collection Summary:

Timing of Measurements

Measurements made in cases and controls and compared.

Dependent Variables

  • Weight, height, BMI
  • REE measured through indirect calorimetry
  • 24-hour urinary nitrogen calculated to correct RQ
  • Body composition measured through bioelectrical impedance and skinfold measurements
  • TNF-alpha measured by ELISA
  • Dietary intake through three-day food records, reviewed by RD. 

Independent Variables

HIV infection.
Description of Actual Data Sample:
  • Initial N: 26 subjects; 10 asymptomatic HIV-infected females, 16 healthy controls
  • Attrition (final N): 10 cases, 16 controls
  • Mean age: Cases, 35±7 years; controls, 34±9 years
  • Ethnicity: Not mentioned
  • Other relevant demographics: Mean CD4 count = 636/mm3
  • Anthropometrics: Controls matched for age, BMI and fat free mass
  • Location: Delaware.
Summary of Results:

  HIV-Infected (N=10)

Controls (N=16)

P-Value
Age (years) 35.2±7.2 33.7±8.6 0.66
Height (cm) 164.5±5.4 164.1±7.7 0.90
Weight (kg) 99.5±33.3 78.1±15.9 0.04
FFM (kg) 56.2±4.3 50.2±6.5 0.14
Fat Mass (kg) 43.3±19.9 27.9±10.0 0.01
Percentage Body Fat 41.6±7.0 34.9±5.7 0.01
BSA (m2) 2.0±0.3 1.8±0.2 0.06

BMI

36.4±11.3

29.2±7.1

0.06

Waist-to-Hip Ratio

0.79±0.04

0.79±0.05

0.70
Absolute REE (kcal/Day) 1,755±410 1,497±197 0.05
REE (kcal/kg) 31.4±1.75 29.9±2.5 0.04
RQ 0.80±0.03 0.79±0.02 0.89
Urinary Nitrogen (g/Hour) 4.7±2.7 7.8±2.9 0.01
Kcal/24-Hours 1,919.7±562 1,903±516 0.94
Kcal/kg/24-Hours 24.7±18.0 26.3±10 0.78
Carbohydrate (g) 209.7±73.1 254.1±96.3 0.23
Carbohydrate (%) 45.3±4.6 54.0±7.9 0.002
Fat (g) 88.4±31.9 64.1±20.3 0.03
Fat (%) 40.6±4.9 30.4±6.3 0.0002
Protein (g) 85.6±35.7 69.6±20.1 0.15
Protein (%) 15.7±3.0 15.2±3.4 0.77

Other Findings

  • Absolute REE was 17% higher (1,755kcal per kg ±410 vs. 1,497kcal per kg ±197) in the HIV-infected group, compared with the control group (P<0.05)
  • REE remained significantly higher in the HIV-infected group when REE was adjusted for body composition differences (P=0.04)
  • Results revealed a 23% higher level of TNF-alpha in the HIV-infected subjects (P<0.01), however only a weak correlation existed between TNF-alpha and REE (R=0.352).
Author Conclusion:
  • The etiology of hypermetabolism is complex and investigations of all possible interventions that will enable the HIV-infected patient to maintain weight are of vital importance
  • Despite the weak correlation between TNF-alpha and REE, it is significant that we found TNF-alpha to be significantly elevated in the asymptomatic HIV-infected female
  • Future research should focus on the interaction of several cytokines that regulate immunity and are involved in metabolism. Longer-term studies inclusive of females could more precisely determine the significant relevance of these cytokines to hypermetabolism. Furthermore, since increased REE and increased levels of proinflammatory TNF-alpha were present in the HIV-infected group, continued research investigating TNF-alpha cytokine inhibitors in the HIV population is suggested.
Funding Source:
Reviewer Comments:
  • Small groups
  • Recruitment methods not described
  • Controls were significantly different for certain baseline characteristics that would affect REE, such as weight.
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? ???
  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? ???
  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? ???
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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  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.) No
  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? 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? 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? 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