H/A: Dietary Intake (2007)
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To investigate the relation between dietary fatty acid intake and liver function in HIV-infected compared with HIV-uninfected subjects.
Inclusion Criteria:
- Apparently healthy black volunteers aged more than 15 years
- Asymptomatic HIV-infected and HIV-uninfected subjects.
Exclusion Criteria:
- Pregnant and lactating women
- Known diagnosed diseases
- Use of chronic medications
- Oral temperatures over 37 degrees Celsius
- Inebriated subjects.
Description of Study Protocol:
- Recruitment: Recruited from 37 randomly-selected sites throughout the North West province of South Africa in 1996 and 1998
- Design: Cross-sectional epidemiological survey.
Statistical Analysis
- Data are presented as adjusted means (95% CIs) for HIV-infected and HIV-uninfected subjects
- Data that were not normally distributed were normalized by logarithmic transformations
- Multivariate analysis was used to compare biochemical variables of HIV-infected and HIV-uninfected subjects
- Partial correlations were used to determine the associations between the intake of dietary fat and vitamin E and the biochemical variables
- Fisher Z-values were calculated for each correlation to test for significant differences in R-values between HIV-infected and uninfected subjects.
Data Collection Summary:
Timing of Measurements
Measurements made and compared.
Dependent Variables
- BMI
- Blood pressure
- Fasting blood samples analyzed for serum protein, albumin, globulin, gamma-glutamyl transpeptidase, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase and lipids
- HIV status.
Independent Variables
Demographic information, physical activity and dietary intake data were obtained during individual interviews by using validated questionnaires.
Control Variables
- Level of urbanization
- Age
- Sex
- Year of study
- Alcohol intake.
Description of Actual Data Sample:
- Initial N: 1,854 healthy black volunteers. Complete data available for 216 asymptomatic HIV-infected (96 male, 120 female) and 1,604 HIV-uninfected subjects (685 male, 920 female)
- Attrition (final N): As above
- Age: HIV-infected subjects' mean age, 34.8 years; uninfected subjects' mean age, 37.9 years
- Ethnicity: All were black
- Other relevant demographics: HIV-infected subjects' mean BMI, 23.7; uninfected subjects' mean BMI, 24.0
- Location: South Africa.
Summary of Results:
Liver Enzymes |
HIV Infected |
HIV Uninfected |
P2 |
GGT | 44.1 (29.3, 58.8) | 39.2 (32.9, 45.6) |
NS |
ALT |
16.8 (14.0, 19.5) |
13.4 (12.2, 14.6) |
0.03 |
AST |
37.0 (28.6, 45.4) |
24.3 (20.7, 28.0) |
0.01 |
ALP | 79.4 (74.3, 84.5) | 77.4 (75.5, 79.3) | NS |
LDH | 148.0 (142.6, 153.3) | 138.9 (136.6, 141.2) | <0.01 |
Other Findings
- Concentrations of total serum protein and globulin were significantly higher, whereas concentrations of total serum cholesterol, HDL cholesterol and albumin were significantly lower in HIV-infected subjects than in uninfected subjects
- Alcohol intake tended to be higher in HIV-infected subjects (P=0.08)
- HIV-infected and uninfected subjects did not differ significantly with regard to BMI, education, smoking or snuff-taking, blood pressure and physical activity
- Intakes of polyunsaturated fatty acids, linoleic acid (n-6) and the ratio of PUFAs to saturated fatty acids were positively associated with all the liver enzymes measured in HIV-infected subjects (R=0.16-0.65).
- Most of these R-values differed significantly from the R-values for HIV-uninfected subjects
- No associations were seen between liver enzymes and intakes of SFAs and monounsaturated fatty acids
- Vitamin E intake was positively associated with serum-gamma-glutamyl transpeptidase (R=0.23), alanine aminotransferase (R=0.37) and aspartate aminotransferase (R=0.58) in HIV-infected subjects. These correlations differed significantly from those of the HIV-uninfected subjects because PUFA sources are the main carriers of vitamin E.
Author Conclusion:
The main observation of this investigation was that the n-6 PUFA intake was adversely related to liver function in asymptomatic HIV-infected subjects, compared with HIV-infected subjects. The reasons or mechanisms responsible are not clear and further research is necessary to determine the optimal safe amounts for intake of n-6 PUFAs by HIV-infected subjects, especially in countries with traditionally high intakes of n-6 PUFA-rich vegetable oils.
Funding Source:
Government: | National Research Foundation (South Africa), SA MRC | ||
Industry: |
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University/Hospital: | North-West University |
Reviewer Comments:
Authors note that since HIV-infected subjects were apparently healthy and asymptomatic, the early stage of HIV infection resulted in absence of significant differences between HIV-infected and uninfected individuals in some parameters.
Quality Criteria Checklist: Primary Research
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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? | N/A | |
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? | 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 | |