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MNT: Comparative Effectiveness of MNT Services (2009)

Citation:

Neil HAW, Roe L, Godlee RJP, Moore JW, Clark GMG, Brown J, Thorogood M, Stratton IM, Lancaster T, Mant D, Fowler GH.  Randomized trial of lipid lowering dietary advice in general practice: the effects on serum lipids, lipoproteins, and antioxidants. BMJ. 1995; 310 (6979): 569-573.

PubMed ID: 7888933
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine the relative efficacy in general practice of dietary advice given by a dietitian, a practice nurse or a diet leaflet alone on serum lipid, lipoprotein and antioxidant concentrations in patients with type IIa or IIb hyperlipoproteinemia.

Inclusion Criteria:
  • Men and women of European origin
  • Aged 35 to 64 years
  • Total cholesterol concentration on screening of 6.5mmol to 9.0mmol per L
  • Repeat total cholesterol concentration of 6.0mmol to 8.5mmol per L.
Exclusion Criteria:
  • Total cholesterol-to-HDL cholesterol ratio under 4.0
  • LDL cholesterol concentration under 3.5mmol per L
  • Fasting triglyceride concentration over 5.6mmol per L
  • Diagnosed diabetes, hypothyroidism or renal disease
  • Current treatment with a lipid lowering drug
  • Admission to hospital with a severe illness within the previous three months
  • Pregnancy or breastfeeding.
Description of Study Protocol:
  • Recruitment: Patients were recruited from a group practice in Oxfordshire with nearly 11,600 patients
  • Design: Randomized six-month parallel trial. Randomization was done by using a list of consecutive random treatment assignments.
  • Blinding used: Not possible.

Intervention

  • Individual advice provided by a dietitian using a diet history (30-minute session), a practice nurse using a structured food frequency questionnaire (30-minute session) or a detailed diet leaflet sent by post
  • All three groups were advised to limit the energy provided by fat to 30% or less, consume up to 10% of energy from saturated, monounsaturated and polunsaturated fatty acids, to increase carbohydrate (50% to 60%) and dietary fiber (35g) and 300mg cholesterol
  • Subjects in the dietitian and nurse intervention groups were reviewed eight weeks after the initial visit and further advice was given during a 10-minute session
  • Subjects in the diet leaflet group received additional written advice two months after the initial visit.

Statistical Analysis

  • Trial was designed to have a 90% statistical power to detect a difference of more than 0.3mmol per L between the groups in mean total cholesterol concentration at the end of the trial, with a 5% level of significance
  • Data analyzed on basis of intention to treat
  • For continuously distributed variables, statistical comparisons between groups were made by ANOVA
  • ANOVA was also used to examine differences between groups in the mean individual changes from baseline to end of trial
  • Comparisons between groups were made by paired T-tests
  • Chi-square test was used to test for differences between categorical variables.
Data Collection Summary:

Timing of Measurements

Measurements made at baseline and after six months.

Dependent Variables

  • Weight, BMI
  • Concentrations of total cholesterol, HDL cholesterol and triglycerides measured with standard laboratory methods
  • LDL cholesterol concentration calculated using Friedewald equation
  • Serum concentrations of retinol, alpha-tocopherol, lutein, cryptoxanthin, lycopene and alpha and beta carotene, measured in duplicate using high-performance liquid chromatography.

Independent Variables

  • Individual advice provided by a dietitian using a diet history, a practice nurse using a structured food frequency questionnaire or a detailed diet leaflet sent by post
  • Subjects were given a brief questionnaire for self completion which asked about the dietary changes they had made.
Description of Actual Data Sample:
  • Initial N: 2004 subjects screened for hypercholesterolemia; 309 (163 men and 146 women) entered the trial
  • Attrition (final N): 20 randomized patients did not proceed to their allocated intervention and 10 were lost to follow-up.  There were no withdrawals. 279 completed the six-month study.
  • Age: Subjects aged 35 to 64 years; median, 55.4 years
  • Ethnicity: Not reported.

Other Relevant Demographics

  • Anthropometrics: At baseline, there were significantly more smokers in the leaflet group than the other two groups and higher mean total cholesterol levels in the leaflet group than the dietitian group
  • Location: General practice in Oxfordshire.
Summary of Results:

 

  Dietitian Group (N=103)
Baseline
Dietitian Group (N=103)
6 months
Nurse Group (N=104)
Baseline
Nurse Group (N=104)
6 months

Leaflet Group (N=102)
Baseline

Leaflet Group (N=102)
6 months

Total Cholesterol (mmol/L) 7.01±0.61 6.91±0.73 7.15±0.65 6.97±0.74,
P <0.01
7.23±0.63 7.10±0.63

LDL Cholesterol (mmol/L)

5.11±0.60

5.00±0.70 5.17±0.67 4.99±0.69,
P <0.01

5.25±0.65

5.06±0.62,
P<0.01

HDL Cholesterol (mmol/L) 1.18±0.26 1.17±0.26 1.23±0.27 1.28±0.30,
P <0.01
1.23±0.28 1.25±0.30
Triglycerides (mmol/L) 1.48 (range 0.94-2.31) 1.53 (range 0.99-2.37) 1.56 (range 1.01-2.41) 1.46 (range 0.98-2.19),
P<0.05
1.54 (range 0.99-2.41) 1.57 (range 1.01-2.46)

BMI

26.64±4.06

26.40±4.00,
P<0.01
26.31±3.93 26.24±4.22

26.32±4.32

26.08±4.29

Other Findings

  • No significant differences were found at the end of the trial between groups in mean concentrations of lipids, lipoproteins and antioxidants or BMI
  • After data were pooled from the three groups, the mean total cholesterol concentration fell by 1.9% (0.13mmol per L; 95% confidence interval, 0.06 to 0.22; P<0.001) to 7.00mmol per L and LDL cholesterol also fell
  • The total carotenoid concentration increased by 53 mmol per L (95% confidence interval, 3.0 to 103; P=0.039). 
Author Conclusion:
  • In summary, we found no difference in the relative efficacy of lipid-lowering dietary advice given by a dietitian, a practice nurse or a diet leaflet alone. The cost-effectiveness of these interventions will differ substantially.
  • Overall, after allowing for regression to the mean, there was about a 1.5% reduction in the concentration of total cholesterol in asymptomatic, moderately hypercholesterolemic patients, identified by a screening program in general practice. This would be expected to reduce coronary heart disease mortality by 3% to 4%.
  • To obtain a better response, it is probably necessary to use more intensive intervention than is normally available in primary care. Cholesterol testing should therefore be targeted at patients at highest overall risk of coronary heart disease, in whom treatment with lipid-lowering drugs may be warranted if there is an inadequate response to dietary advice.
  • To substantially reduce the mean serum cholesterol concentration of the population as a whole, a national programme is needed.
Funding Source:
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:
  • Trial only lasted six months
  • Significant differences between groups at baseline.
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? 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? 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.) 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? 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? ???
  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? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  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? ???
  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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  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? Yes
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? No
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