EAL

GDM: Monitoring (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To answer the following questions:

1. When does the physiological peak of postprandial glucose occur?

2. Do non-diabetic pregnant women and pregnant women with diabetes have different postprandial glucose profiles?

3. What is the optimal time for postprandial glucose measurement rated according to clinical outcome?

Inclusion Criteria:

Healthy pregnant women seeking prenatal care
Patients diagnosed with GDM and type 1 diabetes
Patients underwent an oral glucose tolerance test with 75 g glucose, which was assessed using the criteria of the German Diabetes Association to determine if they were classified as Pregnancy Complicated by Diabetes or Non-Diabetic Pregnant

Exclusion Criteria:

None specifically mentioned. Data from subjects were excluded if meal logs were incomplete or if their sensor malfunctioned.

Description of Study Protocol:

Recruitment

Patients recruited from the clinic between July 2000 and January 2001.

Design: Cohort study

Blinding used (if applicable): Not applicable

Intervention (if applicable)

Patients with carbohydrate intolerance underwent dietary counseling in accordance with the recommendations of the American Diabetes Association
Patients received a CGMS for use over 72 hours
Groups were divided according to 3 clinical outcome parameters: mode of delivery, birth weight percentile, and diabetes-associated complications.

Statistical Analysis

For statistical analysis of non-normally distributed data, the non-parametric Mann-Whitney U test was used, and for nominal data the chi-square test was used. The group sizes were large enough to guarantee a power of 80% to detect an effect size of 1.

Data Collection Summary:

Timing of Measurements

Pre- and postprandial glucose levels were documented at 15-minute intervals for 3 hours from the beginning of each meal. The postprandial data from the 3 meals were added.

Dependent Variables

Glucose levels determined using hexokinase method and continuous glucose monitoring
Clinical outcomes: rates of spontaneous and non-spontaneous delivery, birth weight percentile, postnatal hypoglycemia, hyperbilirubinemia, breathing problems

Independent Variables

Pregnancy Complicated by Diabetes or Non-Diabetic Pregnancy

Control Variables

Description of Actual Data Sample:

Initial N: 75 women originally enrolled, 22 had to be excluded due to incomplete meal logs or sensor malfunction

Attrition (final N): 53 pregnant women, 17 with pregnancy complicated by diabetes (13 with GDM, 4 with type 1 diabetes) and 36 non-diabetic pregnant women

Age: mean age non-diabetic pregnancy group: 30 ± 6.0 years, mean age pregnancy complicated by diabetes group: 30 ± 6.4 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics: Statistically significant differences between groups were found for BMI, fetal birth weight and oral glucose tolerance test. No significant differences were found for age, parity and gestational age, mode of delivery and diabetes-associated complications.

Location: Germany

Summary of Results:

	Sum of glucose values at 3 meals, NDP (n=36)	Sum of glucose values at 3 meals, PCD (n=13)	P value
Onset of eating	15.0 ± 2.4	15.3 ± 3.4	0.887
15 minutes	15.8 ± 2.7	16.4 ± 3.7	0.692
30 minutes	16.8 ± 3.1	18.1 ± 3.7	0.229
45 minutes	17.3 ± 3.6	19.2 ± 3.6	0.070
60 minutes	17.6 ± 3.5	19.6 ± 3.9	0.085
75 minutes	17.4 ± 3.4	19.7 ± 3.7	0.080
90 minutes	17.5 ± 3.5	19.1 ± 3.2	0.110
105 minutes	17.4 ± 3.4	18.9 ± 2.7	0.112
120 minutes	17.0 ± 3.2	18.3 ± 2.4	0.048
135 minutes	16.4 ± 2.1	18.0 ± 2.1	0.029
150 minutes	16.7 ± 3.1	16.6 ± 2.9	0.836
165 minutes	15.8 ± 2.0	16.7 ± 2.2	0.357
180 minutes	16.0 ± 2.1	16.7 ± 2.6	0.452

Other Findings

The sensor provided similar numbers of measurements in both groups (278 ± 43 vs. 298 ± 73, P = 0.507).

The postprandial glucose peak was reached after 82 ± 18 minutes in the non-diabetics vs 74 ± 23 minutes in the pregnancy complicated by diabetes group (P = NS).

Postprandial glucose values were normally slightly higher in the pregnancy complicated by diabetes group (P = NS).

For the sum of the postprandial glucose values at each time interval for the 3 meals for each day, there was a significant difference between the measurements at 120 minutes and at 135 minutes postprandial (P < 0.05).

Dividing the group by clinical outcome showed a significant difference between the postprandial time intervals of 75 minutes and 105 minutes (P < 0.05).

In addition, the time interval was different from 60 minutes to 135 minutes for the mode of delivery and birth weight percentile (P < 0.05).

Author Conclusion:

The 120-minute interval is too long and has a lower correlation to clinical outcome parameters than earlier measurements. Our findings show that the optimal time for testing is between 45 and 120 minutes postprandial. Based on our practical experience and dietary recommendations, we would prefer a 60-minute interval, because patients can calculate this more easily and can have more freedom to eat the recommended number of snacks.

Funding Source:

Reviewer Comments:

Some significant differences between groups at baseline, but these differences would be expected between diabetic and non-diabetic pregnancies.

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?		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.)	No
	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?	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?	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?	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)?	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?	Yes
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