NC: Transtheoretical Model (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

  • This study compared diabetes Treatment As Usual (TAU) with Pathways To Change (PTC), an intervention developed from the Transtheoretical Model of Change (TTM)
  • This study is to determine whether the PTC intervention would result in greater readiness to change, greater increases in self-care and improved diabetes control.

Inclusion Criteria:
  • Type 1 and type 2 diabetics not engaging in optimal self-care practices (pre-action)
  • Participants were considered pre-action if:
    • Self-monitoring blood glucose: If they performed SMBG fewer than four times per day if treated with insulin or fewer than two times per day if treated with oral anti-hyperglycemic agents alone
    • Healthy eating: Diet over 30% fat (N=445) and BMI over 27kg per m2
    • If they smoked cigarettes.
Exclusion Criteria:

Patients were ineligible for participation in the study:

  • If they were on diet therapy alone
  • They could not respond to the materials written in English
  • They required more than usual care because of their health status (e.g.,were pregnant or on dialysis)
  • If they had no telephone.
Description of Study Protocol:


A  total of 1,029 individuals with type 1 or type 2 diabetes who were in one of three pre-action stages for either SMBG, healthy eating, or smoking were recruited for this 12-month study. Subjects recruited from posters in local family practices, diabetes education centers, newspaper ads and Canadian Diabetes Association chapter activities. 


This study was a randomized split-plot design with two randomized between-subject factors: Treatment (PTC vs. TAU) and strips (free strips vs. no strips) and one within-subject factor (pre- vs. post-study).

Blinding Used

Not reported. 


Pathways to change [PTC] vs. Treatment as Usual [TAU]

  • PTC is an integrated, multi-component intervention program that provides monthly mail or telephone contact for 12 months
  • The components of the intervention are based on the individual’s current stage of change, as well as stage-matched processes and principles of change
  • A handbook providing general diabetes information and an introduction to the TTM was mailed to PTC participants after recruitment
  • Individual stage was assessed using quarterly assessment surveys, which generated a personal feedback report targeted to each self-care behavior
  • Stage of change was assessed through questions addressing intention to change and current behavior
  • The PTC consisted of stage-matched personalized assessment reports, self-help manuals, newsletters and individual phone counseling, designed to improve readiness for self-monitoring of blood glucose (SMBG), healthy eating or smoking cessation
    • Counselor conducted telephone calls one time per month after the personal report to answer questions, provide tips on behavior change and facilitate personal goal-setting
    • Seven newsletters were sent every other month.

Statistical Analysis

  • Participants who did not complete the study were coded as remaining in pre-action for the intention-to-treat (ITT) analysis
  • The main comparisons were between the proportion of participants in PTC vs. TAU, and free strips vs. no free strips for the SMBG intervention, across the stages (pre-action vs. action and maintenance stages) at end of study
  • Differences in proportions were tested using X2 analysis
  • If main effects of both treatment and strips were significant for the self-testing risk
  • the interaction was analyzed by comparing the outcome for each of the four groups (TAU alone, TAU plus strips, PTC alone and PTC plus strips) using X2 analysis
  • Outcomes for glycemic control (HbA1c), weight, meter memory data and eating behavior were analyzed using repeated- measures ANOVA. The SMBG frequency data per memory meter was coded to obtain an average weekly blood glucose level for Weeks Five to Eight and 49 to 52 of the study
  • Data from Weeks One to Four were not used to minimize any temporary increase in SMBG frequency associated with starting the study.
Data Collection Summary:

Timing of Measurements

12-month study: Protocol called for patients to visit clinic for assessment at baseline and at end of study.

Dependent Variables

  • Healthy eating: Intake measured using a validated food frequency instrument, the NCI Block
  • SMBG: Smoking (TAU and PTC with strips and without strips)
  • HgA1C: Measured from a venous blood sample using an immunoturbidometric method
  • Memory blood glucose meter and phone modem used to send blood glucose results
  • Height, weight and BMI
  • Healthcare utilization information collected at baseline and at 12-month follow-up.

Independent Variables

  • TAU and PTC: Strips and no strips
  • Pre-action, action: Maintenance stages assessed through questions addressing intention to change and current behavior.

Control Variables Treatments

TAU involved regular family physician or endocrinology visits or diabetes education sessions as prescribed. No attempt was made to influence medical management of either group.


Description of Actual Data Sample:

Initial N

  • 1,029
  • Men: 539
  • Women: 490
  • Healthy eating component: 445.

Attrition (Final N)

  • 77% completed one year study 
  • 81.2% completion rate for healthy eating component.


Range: 54 to 55 years.



Other Relevant Demographics

  • A total of 445 participants were in pre-action for healthy eating and 168 participants were in pre-action for smoking. Completion rates were 81.2 and 80.4%, respectively.
  • A total of 58.2% of participants were enrolled for two behaviors (89% of these for both SMBG and healthy eating) and 8.2% of participants were enrolled for three behaviors
  • A total of 860 participants were enrolled for SMBG: 77.7% completed the entire year of the study.   


Strips 31.98 32.22
No Strips 31.43 31.59


  • Two-thirds of the cohort were recruited from Southern Ontario, Canada
  • One-third of the subjects were recruited from Nova Scotia.
Summary of Results:
  • No significant differences in baseline characteristics were observed between the groups
  • 77.7% completed the entire year of the study
  • A total of 445 participants were in pre-action for healthy eating and 168 participants were in pre-action for smoking. Completion rates were 81.2% and 80.4%, respectively. Participants who did not complete the entire 12 months of the study did not have different baseline demographic characteristics from those who did complete the study (data not shown).
  • A total of 58.2% of participants were enrolled for two behaviors (89% of these for both SMBG and healthy eating) and 8.2% of participants were enrolled for three behaviors
  • There was a significant treatment effect for PTC vs. TAU (P<0.001) and for whether or not free testing strips were provided (P<0.002)
  • Differences in favor of PTC are seen for SMBG frequency in those providing end-of-study data (P<0.002). Only PTC participants significantly increased SMBGP (P<0.002).
  • Results for the NCI Block Food Frequency Questionnaire indicated that PTC participants, relative to TAU participants, reported a lower percentage of calories from fat (35.24 vs. 36.1%, P< 0.004) and higher daily vegetable (2.24 vs. 2.06, P<0.011) and fruit servings (1.89 vs. 1.68, P<0.01)
  • Both PTC and TAU participants increased the frequency of injections (P<0.001)
  • More patients in the PTC group participated in diabetes education programs (P<0.002). End-of- study HbA1c for the SMBG intervention was 7.78% for those who reached an action stage, compared with 8.30% in those who stayed in pre-action (P<0.003).
  • 22% of PTC insulin-using participants changed to an insulin analog, as compared with 13% of the TAU group
  • In the healthy eating group, HbA1c was 7.83% for those in action, but remained at 8.38% for those in pre-action (P<0.001)
  • Increased SMBG accounted for 3% of the variance in end-of-study HbA1c level in the non-insulin-treated group (P<0.01) and 7% in the insulin-treated group (P<0.01).





Statistical Significance



TAU 81.6% 10.9% 7.5%


TAU and Strips 73% 17.3% 9.7%  






PTC and Strips

56.6 %




Healthy eating
























·          At baseline, 100% of participants were in pre-action.

  • 10.9% of the TAU group moved to action and 7.5% moved to maintenance, whereas of those receiving testing strips alone, 17.3% moved to action and 9.7% moved to maintenance
  • Of those receiving PTC alone, 12.1% moved to action and 18.4% moved to maintenance
  • When PTC and strips were combined, 10.2% of participants moved to action and 33.2% moved to maintenance (P<0.001)
  • PTC was associated with more movement to action or maintenance than TAU (P<0.001)
  • There were significantly more PTC than TAU patients who quit smoking (17.8% in action and 5.5% in maintenance vs. 11.6% in action and 0% in maintenance, respectively) in the ITT analysis for the 168 enrolled smokers (X2=7.01, P<0.02).
Author Conclusion:
  • This study demonstrates that this intervention has the potential of positively impacting the health of broad populations of individuals with diabetes, not just the minority who are ready for change
  • The PTC intervention has the capacity to deliver effective interventions to a large number of people.
Funding Source:
Reviewer Comments:
  • This study demonstrates significant effect of interventions on SMBG, healthy eating and smoking
  • TAU with strips intervention is better than other intervention on SMBG self-care behaviors
  • TUA intervention is better than PTC intervention for healthy eating behaviors and PTC has significant effect on smoking behaviors
  • However, statistical analysis was not conducted between the intervention
  • The analysis was conducted between the changes in self-care outcomes, healthcare utilization indicators and impact of self-care change. The participants are type 1 or type 2 diabetics.
  • It is not clear whether the interventions had different effects on stage of change in behaviors in type 1 and type 2 DM
  • It is not clear in baseline characteristics how many participants are type 1 and type 2 DM 
  • There is no information on change in carbohydrates
  • It is very interesting that there is a significant change in healthcare utilization indicators of self-care in both treatments
  • The PTC intervention is better than TAU in helping individuals move into action stages of critical diabetes self-care behaviors
  • The PTC intervention helped to change the SMBG and change in low-fat food choices and stop smoking
  • This intervention is very effective to improve the health of diabetes populations.
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? ???
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) Yes
  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.) ???
  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? ???
  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.) ???
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? ???
4. Was method of handling withdrawals described? No
  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%.) ???
  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? ???
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? ???
  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.) ???
  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? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? ???
  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? Yes
  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? Yes
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? 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)? 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? ???
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? ???
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? ???