DM: MNT (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To assess effectiveness of clinical nutrition education in reducing HbA1c levels and to test the relative effectivenss of clinical nutrition education when it was delivered by a registered dietitian (RD) compared with an educator from another discipline (non-RD).
Inclusion Criteria:

From clinical care data collected by Indian Health Service (IHS) Diabetes Care and Outcomes Audit of medical records at 218 different facilities during 2001:

  • ages 18 years or older
  • diagnosis of type 2 diabetes
  • without proteinuria
  • two HbA1c values recorded during the year
Exclusion Criteria:
Not specified
Description of Study Protocol:

Recruitment - records reviewed from data from IHS Diabetes Care and Outcomes Audit of medical records at 218 different facilities during 2001 (methods described previously, listed in references)

Design - Retrospective Cohort.  Clinical care data was examined. Glycemic control was assessed by using the difference between the two most recent HbA1c levels in 2001. Age, BMI, duration of diabetes, type of treatment, proteinuria, and facility were included as covariates.  

Blinding used (if applicable) - not applicable

Intervention (if applicable) - Clinical nutrition education was defined as documentation in the record of any diet instruction and educator discipline classified as RD or non-RD.

Statistical Analysis - ANCOVA methods were used to assess the effects of diet education and educator discipline on differences between the two HbA1c measurements and to adjust for differences in the distribution of covariates among the education groups.

 

Data Collection Summary:

Timing of Measurements - while HbA1c was recommended to be done every 3 months, the audit does not record the time interval. A focused study of the interval between HbA1c values at one large IHS facility was done where computerized lab data were available for analysis, and there was no statistical difference in the mean number of days between the 2 most recent HbA1c values for people who received instruction by an RD and by a non-RD, for patients instructed only by a non-RD, or for patients with no documentation of dietary instruction. 

Dependent Variables

  • HbA1c

Independent Variables

  • nutrition education/instruction by an RD
  • nutrition education/instruction by a non-RD

Control Variables

  • Age (calculate at date of audit)
  • BMI (from recorded height and weight)
  • duration of diabetes  (time since diagnosis in years)
  • type of treatment (diet alone-no medication; oral agent - singly or in combination with other oral agents; or insulin - if oral agents also used, patient was included with insulin group for analysis.)
  • proteinuria defined as having 1+ (30mg/dl) or greater on a urine dipstick in the past year
  • facility 

 

Description of Actual Data Sample:

Initial N: 8,826 (male 2,901 (38.4%), female 4,645 (61.6%)

Attrition (final N): as above

Age: at audit (n=7,490) Mean (SE): 55.2 (13.3)

Ethnicity: American Indian/Alaska Native

Other relevant demographics: BMI (n=7,490) Mean (SE):33.7 (7.3)

Anthropometrics type of treatment: diet alone 868 (11.6%); oral agents 4,760 (63.0%), insulin 1,902 (25.4%)

Location: 218 IHS facilities

 

Summary of Results:

 Adjusted* HbA1c level mean differences (SE) by clinical nutrition education for those receiving diet therapy and oral agent therapies.

N = 7,490

HbA1c mean difference (SE)

95% CI
DIET THERAPY      
diet instruction - yes

 568

 - 0.14 (0.07)

 - 0.28, - 0.01

diet instruction - no

 300

 - 0.02 (0.88)

 - 0.15,   0.20

RD 163  - 0.23 (0.12)a  - 0.47, - 0.02
Both RD and non-RD 95  - 0.18 (0.15)a,c  - 0.48,   0.13
non-RD 310  - 0.10 (0.09)d  - 0.27,   0.07
None 285

   0.04 (0.09)b

 - 0.13,   0.22
Refused 15  -0.30 (.035)  - 0.98,   0.40
ORAL THERAPY      
Diet instruction - yes 3,156  - 0.19 (0.04)a  - 0.27, - 0.11
diet instruction - no 1,564  - 0.02 (0.05)b  - 0.12,   0.08
RD 1,018  - 0.23 (0.06)a  - 0.35, - 0.10
Both RD and non-RD 544  - 0.33 (0.08)a,c  - 0.49, - 0.17
non-RD 1,594  - 0.12 (0.05)d  - 0.22, - 0.02
None 1,487  - 0.01 (0.05)b  - 0.11,   0.09
Refused 77  - 0.17 (0.19)  - 0.54,   0.20

*Adjusted for age, sex, duration of diabetes, BMI, initial HbA1c level, and clinical facility; a,b and c,d are statistically significantly different by Tukey's studentized range (honestly significant difference).

Other Findings

Overall, clinical nutrition education was associated with improving HbA1c values during 2001.

When analyses were stratified by type of treatment, all clinical nutrition education groups had improvement in HbA1c compared with those receiving no education among patients treated with diet and exercise alone, or oral agents. This was statistically significant for those receiving oral therapies (P< 0.0001).

None of the clinical nutrition education groups showed improvements in HbA1c values among patients receiving insulin therapy.

 

Author Conclusion:

Although data are consistent with the possibility that dietary education by an RD results in improved glycemic control outcomes in patients with diabetes, this was an observational study, and causality cannot be assigned to the associations identified.

Funding Source:
Government: Indian Health Service
University/Hospital: Phoenix Indian Medical Center, University of California
Reviewer Comments:
A clearly described study, with descriptions of how variables were accounted for, and with a good discussion of limitations.
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? ???
  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? 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? 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.) 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? N/A
  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? N/A
  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? 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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? No
  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? 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? N/A
  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? ???
  10.2. Was the study free from apparent conflict of interest? Yes