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GDM: Self-monitoring of Glucose (2001)

Citation:

Schmidt MI, Duncan BB, Reichelt AJ, Branchtein L, Matos MC, Forti AC, Spichler ER, Pousada JMDC, Teixeira MM, Yamashita T, for the Brazilian Gestational Diabetes Study Group.  Gestational diabetes mellitus diagnosed with a 2-hour 75-g oral glucose tolerance test and adverse pregnancy outcomes.  Diabetes Care 2001;24:1151-1155.

Worksheet created prior to Spring 2004 using earlier ADA research analysis template.
PubMed ID: 11423494
 
Study Design:
Cohort Study
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To evaluate American Diabetes Association and World Health Organization diagnostic criteria for gestational diabetes mellitus against pregnancy outcomes.

Inclusion Criteria:
  • >20 yr of age
  • 20 to 28th wk of gestation
  • Negative history of diabetes mellitus outside of pregnancy
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

Brazilian Gestational Diabetes Study was a cohort study conducted in general prenatal care clinics of the National Health Services in 6 Brazilian state capitals.

Design:  Cohort Study

Blinding Used (if applicable):  not applicable

Intervention (if applicable):

  • Questionnaire to obtain demographic information.
  • Anthropometric measurements
  • 2-hr, 75 g OGTT after 12 to 14 hr of fasting (Fasting, 1 and 2 hr plasma glucose)
  • Followed subjects through delivery and the in-hospital postpartum period via chart review.
  • Decisions regarding treatment of hyperglycemia left to clinical judgment of patient’s attending obstetrician. 

GDM defined by plasma glucose (2 abnormal values for ADA criteria)

  ADA WHO
  Mmol/L  
Fasting > 5.3 >7.0
1-hr >10.0  
2-hr >8.6 >7.8

Statistical Analysis

Since macrosomia and preeclampsia were not rare events, crude and adjusted odds ratios estimated by logistic regression were transformed to relative risks for all outcomes.

Data Collection Summary:

Timing of Measurements:

Measurements made during 20 to 28th wk of gestation.

Dependent Variables:

  • Macrosomia defined by birthweight >90th % for age.
  • Preeclampsia defined by hypertension after the 20th wk of gestation associated with proteinuria or convulsions regardless of whether it was of new onset or superimposed upon chronic hypertension.
  • Perinatal death defined by:
    • Fetal loss of >1 kg or
    • >28 wk gestation
    • or early neonatal death (up to 7 days)

Independent Variables

  • Anthropometric measurements
  • 2-hr, 75 g OGTT after 12 to 14 hr of fasting (Fasting, 1 and 2 hr plasma glucose)

Control Variables

Description of Actual Data Sample:

Initial N:  5,564 consecutive women were enrolled from May 1991 – August 1995.

Attrition (final N):  4,998 women completed the scheduled OGTT (90%).  21 women excluded because of diagnosis of diabetes outside of pregnancy.

Age:  33.1% were aged 20 - 24 years, 31.8% were aged 25 - 29 years, 35.1% were aged over 30 years

Ethnicity:  44.9% White, 41.1% Mixed, 13.6% Black, 0.4% Other

Other relevant demographics:

Anthropometrics:

Location:  Brazil

Summary of Results:

Other Findings

GDM based on ADA criteria was diagnosed in 119 women (2.4%, 95% CI, 2.0-2.9 %). Of those, 0.9% had macrosomic infants, 4.8% had preeclampsia and 4.8% resulted in perinatal deaths.

GDM based on WHO criteria was diagnosed in 357 women (7.2%, 95% CI, 6.5-7.9 %).  Of those, 4.0% had macrosomic infants, 7.9% had preeclampsia and 4.5% resulted in perinatal death.

Only 97 cases (81% of total ADA cases and 27% of total WHO cases) were positive by both ADA and WHO criteria.

Women classified only by WHO criteria had lower fasting (5.0 vs. 5.7 mmol/l; P<0.001) but higher 2-hr (8.3 vs. 6.5 mmol/L; P<0.001) plasma glucose values than women classified only by ADA criteria.

Of women positive by WHO criteria, 260 (73%) were negative by ADA criteria.  Conversely, 22 (18%) of the women positive by ADA criteria were negative by WHO criteria.

After adjustment for the effects of age, obesity and other risk factors, GDM by ADA criteria predicted an increased risk of macrosomia (RR 1.29, 95% CI, 0.73-2.18), preeclampsia (2.28, 1.22-4.16) and perinatal death (3.10, 1.42-6.47)

And by WHO criteria predicted an increased risk of macrosomia (1.45, 1.06-1.95), preeclampsia (1.94, 1.22-3.03) and perinatal death (1.59, 0.86-2.90).

None of the women with GDM were treated with insulin, however, 12 were treated with diet.

Author Conclusion:

GDM detected by a 2-hr, 75-g OGTT as defined by ADA or WHO criteria, was associated with the development of adverse pregnancy outcomes. These two criteria are valid options for the detection of a glucose tolerance state predictive of adverse pregnancy outcomes. Assuming that effective treatment is available, the WHO criteria, by identifying a larger number of cases, may have greater potential for prevention.

Funding Source:
Government: Brazilian Ministry of Health,foundation for the support of research of state of rio grand do sul, Brazillian National Council for Technologic and scientific, Pan-American Health Organization (U.N.)
Industry:
Becton Dickinson, Bayer do Brazil
Pharmaceutical/Dietary Supplement Company:
Other:
Not-for-profit
1
Foundation associated with industry:
Reviewer Comments:

The subjects in this study were less affluent and may not be generalizable to more affluent populations.

Although GDM was diagnosed, it did not appear that treatment with diet or insulin was part of usual care, thus, these results would reflect poor outcomes without these interventions.

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? Yes
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%.) 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? 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? 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? 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? 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? N/A
  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? 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? N/A
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