EAL

DF: Cardiovascular Disease (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether differences in apolipoprotein E (apo E) phenotypes influence the response to dietary changes aimed at reducing serum lipids levels by a standardized high-fiber diet.

Inclusion Criteria:

Participants of a two-week metabolic dietary trial that involved either wheat or oat bran supplementation
Have undergone either a colonoscopy without polyp or other abnormality or one or more colonic poly removed at the time of the colonoscopy.

Exclusion Criteria:

Patients receiving lipid-lowering medications

Description of Study Protocol:

Recruitment

Not described

Design

Randomized study of 71 patients to test wheat or oat bran fiber supplementation at a level of 6.8g fiber per 1,000kcal of the diet with a maximum daily intake of 16.4g. Diets were fed at one of the four following caloric levels: 1,600, 2,000, 2,400, or 2,800kcal per day.

Blinding Used

Not applicable

Intervention

Subjects were randomly assigned to consume either a oat or wheat supplements in addition to the basic diets given for two-weeks. A three-day rotating menu was given, taking into account food preferences of the patients.

Statistical Analysis

Regression Analysis

Data Collection Summary:

Timing of Measurements

The following data was collected at pre and post intervention:

Serum Total Cholesterol
Serum LDL Cholesterol
Serum HDL Cholesterol
Serum Triglycerides
Apo A
Apo B
Body Weight.

Dependent Variables

Serum Total Cholesterol
Serum LDL Cholesterol
Serum HDL Cholesterol
Serum Triglycerides
Apo A
Apo B
Body Weight.

Independent Variables

Fiber intake
35 patients have undergone either a colonoscopy without polyp or other abnormality
32 have had one or more colonic poly removed at the time of the colonoscopy (control).

Description of Actual Data Sample:

Initial N: N=71 (Male, Female on Described)
- Six women were taking thyroxin and three menopausal women were taking hormone replacement therapy; none of the premenopausal women were taking oral contraceptives
- Three patients were taking hydrochorothiazide, and three were taking B-Blocking agents
- 35 patients have undergone either a colonoscopy without polyp or other abnormality
- 32 have had one or more colonic poly removed at the time of the colonoscopy
Attrition: N=67
- 43 men
- 24 women
Age: 56.6±12 years
Ethnicity: Caucasian
Anthropometrics: BMI 25.6±2.5
Location:
- St. Michael's Hospital, Toronto, Canada
- Departments of Nutritional Sciences and Preventative Medicine, University of Toronto, Canada.

Summary of Results:

In paired comparisons, a significant difference was seen in the adjusted changes in LDL cholesterol levels between E2 carriers (0.60±0.14mmol/L) and E3 homozygotes (0.21±0.07mmol/L, P=0.014).

In men, the unadjusted decreases in LDL cholesterol levels were statistically significant on both dietary periods.

Oat bran: 0.56±0.13mmol/L, P=0.0002, n=24
Wheat Bran: 0.02±0.0195, n=19

The mean decrease over both metabolic periods for men (0.42± 0.08mmol/L, n=43) was statistically significantly from the corresponding value for women (0.08± 0.11mmol/L, n=24; P=0.12).

Author Conclusion:

This study demonstrates that there is a great sensitivity to the apolipoprotein E (apo E) 2 phenotype in reducing serum LDL cholesterol levels by a standardized high-fiber diet compared to the other allele groups. The data also supports a lipid-lowering advantage of oat bran over wheat bran.

Funding Source:

Reviewer Comments:

Limited presentation of demographic data
Limited presentations of genotypes
No power calculation presented
No description of diet composition
No description of diet tolerance
Sex differences in dietary responsiveness
Analyzed results did not differentiate between the patients that have undergone either a colonoscopy without polyp or other abnormality or one or more colonic poly removed at the time of the colonoscopy.

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?	N/A
	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?	No
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)	No
	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.)	No
	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?	No
	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?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	Yes
5.	Was blinding used to prevent introduction of bias?		No
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	No
	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?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	No
	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?	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?	N/A
	7.5.	Was the measurement of effect at an appropriate level of precision?	N/A
	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?		No
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	No
	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)?	No
	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?	No
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