EAL

H/A: Dietary Intake (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether protein intake is independently associated with body cell mass (BCM) in clinically weight-stable HIV-infected patients.

Inclusion Criteria:

Men who were participating in the CPCRA 039 study: Entry criteria and study procedures for 039 are described in Ref. 16 (Gilbert et al, 1999; J Acquir Immune Defic Syndr. 22: 253-259)
Baseline dietary recall data must have been available.

Exclusion Criteria:

No exclusion criteria given
Women not included because the number of women participating in the CPCRA 039 trial was insufficient to draw statistically valid conclusions concerning the question posed in this study on protein intake.

Description of Study Protocol:

Recruitment

Men were already participating in the CPCRA 039 trial
Available baseline dietary recall data.

Design

Cross-sectional study of baseline dietary recall data collected from the CPCRA 039, a multi-center, randomized, open-label nutritional supplementation study.

Intervention

Not applicable; only analyzed baseline dietary data prior to start the start of supplementation.

Statistical Analysis

Stepwise multiple regression with backward elimination was used to determine which variables were associated in the the presence of other variables in the regression model
Starting list of variables included:
1. Age (years)
2. Weight (kg)
3. Height (m)
4. Three variables for race and ethnicity categories
5. Prior injection drug use (IDU)
6. MBA (seven levels)
7. CD4 cell count
8. Number of prior AIDS-related diagnoses (ARD) events
9. Treatment with protease inhibitor at baseline
10. Total protein intake (grams per day)
11. Animal protein intake (grams per day)
12. Vegetable protein intake (grams per day)
13. Carbohydrate intake (grams per day)
14. Fat intake (grams per day).
A variable remained in the model if its associated significance level in the final model was below 0.05.

Data Collection Summary:

Timing of Measurements

Baseline measurements: Overall study was conducted from July 31, 1996 through November 30, 1997.

Dependent Variables

Body composition measured using a single-frequency bioelectrical impedance analysis (BIA)-101Q analyzer, computed BCM (body cell mass), TBF (total body fat) and ECM (extracellular mass).

Independent Variables

Height and weight, measured following a standard procedure
Macronutrient intake was assessed from a single 24-hour dietary recall using the Minnesota Nutrition Data System NDS-93, Food Database version 11A, Nutrient Database, version 26
Muscle-building activity (MBA): Participation in MBA during the month before enrollment was assessed by a specially prepared questionnaire. Patient rated his level of MBA at one of seven levels: No regular activity (two levels), some activity not involving a training program (two levels) or regular participation in a weight-training program (three levels). Validity of questionnaire confirmed in a pilot study.

Control Variables

Multiple regression analyses; therefore, control variables were included in the analyses.

Description of Actual Data Sample:

Initial N: 467
Attrition (final N): Cross-sectional study; no attrition
Age: 40.4±8.2 years (mean±SD)
Ethnicity
- Latino-Hispanic: 14.8%
- African-American: 36.4%
- White: 45.4%
- Other: 3.4%.
Other relevant demographics
- 19.5% of patients had a history of injection drug use
- HIV disease/therapeutic
  - Karnofsky score: 89.4%±8.1
  - History of AIDS-related diseases: 54.8%
  - Prior ARD events (N): 0.8±0.9
  - CD4⁺ cell count (N/mm³): 103.6±58.3
  - Treated with a protease inhibitor: 73.9%
  - Treated with an antiretroviral and not treated with a protease inhibitor: 22.3%
  - In discussion, it was stated all patients were aymptomatic and weight stable.
Anthropometrics
- Only one group
- Height (m): 1.8±0.1
- Weight (kg): 72.3±9.9
- Body mass index (kg per m²): 23.4±2.6
- Body cell mass (kg): 28.2±3.6
- Total body fat (kg): 12.2±4.2
- Extracellular mass (kg): 31.9±3.4.
Location: Multi-center study; locations not given in this paper.

Summary of Results:

Table Two: Regression Coefficients from the Multiple Regression of Body Cell Mass, Total Body Fat and Extracellular Mass on Variables in the Final Model of Backward Regression Analysis

The variables shown were selected in the final models.

Variables	Body Cell mass	Total Body Fat	Extracellular Mass
Weight, kg	0.28^c	0.45^c	0.27^c
Height, m	4.53^c	-14.19^c	9.78^c
MBA level (1=lowest, 7=highest)	0.28^c	-0.23^c	-0.07^a
Age, 10 years	-0.42^c		0.46^c
African-American (1=yes, 0=else)	0.37^a		-0.51^c
Prior ARD events, N	-0.34^c		0.25^c
Protein intake, 100g	0.68^c		-0.44^c
Carbohydrate intake, 100g	-0.12^a		0.11^b

^a P<0.05
^b P<0.01
^cP<0.001.

Other Findings

18% reported regularly participating in a weight-training program
28% reported regularly performing some strength-building exercises
53% reported not regularly participating in any program
Animal and vegetable protein were determined to be nearly equivalent in their associations with BCM. Therefore, total protein intake was used
CD4 cell count did not remain in any model tested and was not included as a variable in the multiple regression analysis.

Author Conclusion:

Although this study supports an independent association between protein intake and BCM, we cannot conclude from the present data that increasing protein intake will lead to clinically important increases in BCM.

Funding Source:

Government:

National Institute for Allergies and Infectious Disease, Terry Beirn Community Program

Reviewer Comments:

Limitations as mentioned by the authors:

Only HIV-infected patients; no HIV-negative controls
Use of 24-hour dietary recall
Only one method was available to assess BCM
Authors stated a longitudinal, randomized, prospective trial examining the role of protein intake in maintaining BCM in weight-stable HIV-infected patients conducted within the context of careful scrutiny of antiretroviral and opporunistic infection prophylactic therapy is required to confirm these results.

The authors addressed limitations that were a concern for this reviewer.

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)	Yes
	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)	Yes

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?	N/A
	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?		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?	N/A
	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%.)	N/A
	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?		???
	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.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	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?		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?	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