DM: Blood Glucose Self-Monitoring (2007)

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

To determine if real-time, prospective, long-term continuous glucose monitoring can decrease time spent in the hyperglycemic range and increase time spent in the desired range without increasing the time spent in the hypoglycemic range.

Inclusion Criteria:
  • type 1 diabetes
Exclusion Criteria:
None given.
Description of Study Protocol:

Recruitment

Not provided

Design

To compare hyper- and hypoglycemia , in 15 individuals with type 1 diabetes wearing implanted long-term continuous glucose sensors, during blinded (data not displayed to subjects or physicians) vs unblinded (data presented to subjects and alerts set) periods (~44-50 days for each period).

Blinding used (if applicable): Yes

Intervention (if applicable)

Period A. Start-up period: Sensor implantation and calibration 

Period B. Blinded phase (50±16 days), the calibrated sensor calculated sensor glucose measurements (every 30 seconds) and the values were stored in the receiver memory; however readings were NOT made available to subject or physician. Subjects obtained SMBG values a minimum of two times per day and treated with insulin as advised by their health care providers.   

Period C. Unblinded phase (44±17 days), the receiver display was activated so that patients and their health care providers could see real-time glucose values and glucose trend graphs for the previous 1, 3, or 9 hours.  Alerts producing vibratory and auditory signals were also activated.  No instructions were provided to the subject on how to utilize the continuous glucose information, and investigators did not make major therapeutic changes based on the data due to the investigational nature of the device. 

Statistical Analysis

  • Paired values from sensor and SMBG meter in home setting were compared using Deming regression
  • Median difference of time spent in a given glucose range between phases - one-sided Wilcoxon's signed-rank test
Data Collection Summary:

Timing of Measurements

Continuously (every 30 seconds) during the blinded and unblinded periods

Dependent Variables

  • Hypoglycemia - long-term implantable glucose sensor and accompanying receiver (DexCom, San Diego, CA)
  • Hyperglycemia - same as above

Independent Variables

  • type 1 diabetes

Control Variables

  • A1c - method not provided

 

Description of Actual Data Sample:

Initial N: 9 women and 6 men with type 1 diabetes

Attrition (final N): none

Age: 37 years ± 11

Ethnicity: 12 Caucasian, 2 Hispanic, 1 African American

Other relevant demographics:

  • duration of diabetes (years) - 21±11 years
  • Insulin prescription - 8 on pump; 7 on multiple daily injections

Anthropometrics: BMI (kg/m2) - 24.3±3.8

Location:

  • Barbara Davis Center for Childhood Diabetes, University of Colorado, Denver
  • Diabetes & Glandular Disease Research Associates, San Antonio, TX
  • University of California, San Diego

 

Summary of Results:

 

Variables

Baseline (n=15)

Mean±SE

End of study (n=14)

Mean±SE

A1c (%)

7.41±0.004 7.33±0.003

Other Findings

Subjects spent a median of 47% less time below 3.1 mmol/L (P<0.05) and 25% less time above 13.3 mmol/L (P<0.05) during the nonblinded study period compared with the blinded control period.

Author Conclusion:
The availability of real-time continuous glucose values may help patients reduce their hyperglycemic excursions and lower the risk of hypoglycemia.
Funding Source:
Reviewer Comments:
  • To be able to observe glucose values and trends in real-time over long periods, and at home, has got to be an awesome experience for people with diabetes!
  • Changes in glycemic levels observed could potentially be attributed to the Hawthorne effect (high frequency [weekly] of visits to health care professionals compared with routine patient care)
  • Inclusion/exclusion criteria and recruitment methods not well defined, small sample size
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) ???
 
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? No
  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? N/A
  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? 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%.) 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? 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? 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? ???
  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? 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? Yes
  10.2. Was the study free from apparent conflict of interest? Yes