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GDM: Monitoring (2008)


Langer O, Mazze RS.  Diabetes in pregnancy:  Evaluating self-monitoring performance and glycemic control with memory-based reflectance meters.  Am J Obstet Gynecol 1986;155:635-7. 

PubMed ID: 3752183
Study Design:
Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The purpose of the study was to determine the reliability and accuracy of patient self-monitoring of blood glucose during pregnancy.


Inclusion Criteria:

Pregnant women with gestational or pregestational diabetes between the 16th and 39th weeks gestation.

Exclusion Criteria:

None stated.


Description of Study Protocol:


Recruitment methods not defined.


Cohort Study. 

Blinding Used (if applicable):

Subjects were blinded to the memory modification of the glucometer.

Intervention (if applicable):

Study participants were treated with multiple injections of mixed insulins or diet alone.

All subjects were taught and evaluated for self-monitoring techniques in the use of a Glucometer Reflectance Photometer.

The Photometer was modified with a microchip capable of storing 440 glucose values with the corresponding time and date.

Women were asked to maintain careful logbook records during a 14 day study period and to measure capillary blood glucose values at least 7 times/day.

At weekly clinic visits, the accuracy of the meters were checked against lab assays of matched venous samples.

Statistical Analysis:

Performance was measured by comparision between the memory meter and logbook recoreds.

Coefficient of variation was used to determine the difference between the mean for the logbook records and the memory meter.

Performance was evaluated based on type of diabetes, previous outcome of pregnancy, gestational week or type of diabetes therapy (insulin vs. diet)

Data Collection Summary:

Timing of Measurements:

14 day study period women measured capillary blood glucose values at least 7 times daily and to record values in log book.

Dependent Variables:

  • Capillary glucose values recorded in logbook

Independent Variables:

  • Capillary blood glucose values stored in memory meter

Control Variables:

  • Controlled for gestational or pregestational diabetes
Description of Actual Data Sample:

Initial N:  34 women, 21 with gestational diabetes, 13 with pregestational diabetes

Attrition:  34 women

Age:  Mean 30 years + 5

Ethnicity:  Not available

Other Relevant Demographics:

Married, high school graduates, 50 % (N=17) having attended college

Past obstetric history:

34%  spontaneous abortions

11 % premature neonates

23% pregnancy-induced hypertension

17% history of still-birth


Location:  New York

Summary of Results:

Other Findings

97% of the subjects omitted from their logbook records glucose values that were recorded in the meters.

The average underreporting score was 23%+18% (or approximately 1 recording not reported for every 5 values).

The average overreporting score was 23% +31%.

There was a signficant correlation between overreporting and underreporting (r =0.44, p= 0.01).

13 patients achieved 100% precision but this was not related to reliability.

The mean precision score was 88% (range of 53% - 100%).

The mean memory values were 10 mg/dl above the log records (P<0.05).

A significant difference (p= 0.0004) was found between the mean coeffecient of variation for the logbook records (31% + 12%) and the memory meter (39% + 14%).

There was no signficant differences in the relationship between glycemic control as recorded in the meter and performance as determined by overreporting and underreporting.

There were no significant relationships between hemoglobin A1 or random laboratory blood glucose values were compared with performance.

Type of diabetes (gestational vs. pregestational) was not related to performance.

There were no signficant differences between perfomance and previous outcomes of pregnancy or between performance and obesity.

There was no signficant relationship between gestational week and overreporting, underreporting or precision. There was also no signficant difference in therapy (insulin vs. diet) compared to performance.

Author Conclusion:

Self-glucose monitoring was unpredictable and may be unreliable among presumably well-motivated women. 

For 80% of the subjects, significant differences existed between mean blood glucose and coefficient of variation when memory meter and logbook values are compared with a tendency toward a narrowing of the range of reported glucose values.  This resulted in a masking of acute and chronic hyperglycemic episodes.  Inaccurate records will make it difficult to make adjustments in diet and/or insulin to regulate blood glucose.


Funding Source:
Government: NIH
Ames Division of Miles Laboratory
Pharmaceutical/Dietary Supplement Company:
Reviewer Comments:

This study shows the importance of using memory-based meters for measurement of blood glucose in women with gestational diabetes. Most of the data was not shown but just reported.  Recruitment methods not well defined.  Statistical methods not well described. 

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? No
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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) 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? 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? Yes
  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? Yes
  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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  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? ???
  6.6. Were extra or unplanned treatments described? ???
  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? ???
  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? ???
  8.1. Were statistical analyses adequately described and the results reported appropriately? ???
  8.2. Were correct statistical tests used and assumptions of test not violated? ???
  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)? N/A
  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? 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