DM: Blood Glucose Self-Monitoring (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine glycemic control in patients with insulin-treated diabetes after adjustments to the diabetes management plan based on either continuous glucose monitoring or frequent self-monitoring of blood glucose.
Inclusion Criteria:
  • insulin treated diabetes
  • inadequate metabolic control (HbA1c > 7.9%)
  • ages 19-76 yrs
Exclusion Criteria:
None given
Description of Study Protocol:

Recruitment

Subjects recruited prospectively from 7 diabetes centers in the US from January to September, 2000.

Design

Comparison, by method used for adjustment of patient diabetes management plan (SMBG or CGMS), of HbA1c  measured at baseline and 8 and 12 weeks in 109 adults with diabetes (most with type 1). 

 Blinding used (if applicable)

Investigators were blinded to randomization sequence; neither investigators/patients blinded to HbA1c results.

Intervention (if applicable)

Both groups performed SMBG at least 4 times/day for twelve weeks. In addition the CGMS group wore the monitors for 3 days at week 1 and week 3.  Downloads of SMBG and SMBG+CGMS at visits 3 and 5 were used to adjust diabetes management plans.  At week 12 both groups wore the CGMS for 3 days to determine frequency and duration of hypoglycemia and hyperglycemia. 

Statistical Analysis

  • Power calculations based on results of a 5-wk pilot study
  • Repeated-measures analysis of variance used to test for a change from baseline HbA1c
  • Independent t tests to compare frequency and duration of hypoglycemia between the 2 groups
Data Collection Summary:

Timing of Measurements

Baseline, 8 weeks, 12 weeks. 

Dependent Variables

  • HbA1c (method not described)
  • Duration of hypoglycemia: a sensor glucose value of 60 mg/dL or less, with the end of the event as absence of hypoglycemic sensor readings for 30 min or longer.
  • CGMS by Medtronic MiniMed, Northridge CA; Solution Software by same company
  • SMBG by OneTouch FastTake, Lifescan, Milpitas, CA

Independent Variables

  • duration of diabetes
  • type of diabetes

 Control Variables

  • method of insulin delivery

 

Description of Actual Data Sample:

Initial N: 128 subjects:

Attrition (final N):  109 subjects: 19 men and 32 women in the CGMS group; 25 men and 33 women in the SMBG group

Age: CGMS: 44.0±10.2 yrs; SMBG group: 44.5±12.6 yrs

Ethnicity: CGMS: 44 white, 7 other; SMBG: 48 white, 10 other

Other relevant demographics:

  CGMS group SMBG group
Duration of diabetes (yrs) 20.4±10.7 19.5±11.9
Type of diabetes*

46 type 1

5 type 2

51 type 1

5 type 2

Method of insulin delivery

25 CSII

25 MDI

25 CSII

33 MDI

*type of diabetes not declared by 2 individuals

Anthropometrics: weight for CGMS group: 77.0±18.4 kg; weight for SMBG group: 76.9±15.9 kg

Location:

  • Brody School of Medicine, Greenville NC
  • Atlanta Diabetes Associates, Atlanta GA
  • Mountain Diabetes & Endocrine Center, Asheville NC
  • MCP Hospital, Philadelphia PA
  • University of Southern California, Los Angeles
  • University of Chicago, Chicago, IL

 

Summary of Results:

 

Variables

CGMS Group

n=51; mean±SD

SBMG

n=58; mean ±SD

Statistical Significance between groups

Baseline HbA1c (%)

9.1±1.1

9.0±1.0

 NS

8 week HbA1c (%)

8.3±0.9*

8.3±0.9*

 NS

12 week HbA1c (5)

8.3±0.9*

8.3±0.9*

 NS

 *P<0.001 for improvement in both the CGMS and the SMBG groups from baseline to values at week 8 and week 12.

Other Findings

CGMS downloads at 12 weeks indicated hypoglycemic readings for both groups.  The mean duration of hypoglycemia was significantly different between groups: 49.4±40.8 minutes/event in the CGMS group and 81.0±61.1 min/event in the SMBG group (P=0.009). 

Author Conclusion:
Use of the CGMS to guide therapy adjustments in patients with insulin-treated diabetes reduces the duration of hypoglycemia compared with therapy adjustments guided by SMBG values alone.
Funding Source:
Reviewer Comments:
  • One of the few studies to provide power analysis
  • no description or tracking of possible confounding variables - change in diet, change in exercise, etc
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? ???
  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? 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) 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.) 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? Yes
  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? 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.) No
  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? 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? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  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? 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? N/A
  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? No
  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)? No
  8.6. Was clinical significance as well as statistical significance reported? ???
  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? ???
  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