EAL

GDM: Medical Nutrition Therapy (2016)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether nutrition care delivered by registered dietitians (RDs) using nutrition practice guidelines for gestational diabetes (GDM) result in different care and better pregnancy outcomes compared with usual nutrition care provided by RDs.

Inclusion Criteria:

Clinics:

RDs provided clinical nutrition care
>=5 referrals for GDM expected in the following 6 months

Study participants:

Women between the ages of 18 to 45 years old
Singleton pregnancy
Diagnosed with GDM using a standard test

Exclusion Criteria:

Clinics - no other criteria specified

Study Participants:

Pre-existing condition of type 1 or type 2 diabetes; sickle cell anemia, thalassemia, or other hemoglobinopathy; a serious medical condition such as lupus, preexisting hypertension, thyroid disease, cardiovascular disease, transplants, or renal disease
Current infectious disease such as human immunodeficiency virus or tuberculosis.

Description of Study Protocol:

Recruitment

Clinics: 25 clinical sites, including diabetes clinics (n=13), obstetrics clinics (n=4), and other clinics (n=8), from 20 states across the United States were randomly assigned to a group: 12 to nutrition practice guidelines and 13 to usual care.

Study Participants: All eligible women were invited to participate in the study.

Design

The GDM nutrition guidelines and study procedures and forms were mailed to sites in the nutrition practice guidelines arm of the study. Usual care sites received the study procedures and forms only.

Blinding used (if applicable): None mentioned

Intervention (if applicable)

Clinics administered care based on randomization assignment: either adhering to the nutrition practice guidelines or usual care. Pregnant women were enrolled approximately 1 week after GDM diagnosis and followed up until delivery, which was approximately 9 weeks later.

The nutrition practice guidelines for GDM emphasized three major areas:

Definition of MNT clinical goals for the individual (fasting and postmeal blood glucose levels, weight gain/change, urine ketones, and nutrient intake), use of indexes to advance or modify MNT, and criteria to start insulin.
All women were to be taught to self-monitor blood glucose and to keep blood glucose records; follow a food plan and complete food records; and test urine ketones as appropriate for each woman.
Criteria for minimum of three nutrition visits; follow-up contacts could be in person or via telephone or fax.

Statistical Analysis

Descriptive characteristics of clinics, RDs, and participants and nutrition care practices were compared between groups using χ² and t tests.
Multivariable regression analyses
The test of the nutrition care group effect on women’s glycated hemoglobin change was done using multivariable linear regression with estimation via generalized estimating equations to account for the within-clinic correlation in treatment response.
Logistic regression with generalized estimating equations to account for the randomized clusters (clinic site) was used to determine factors related to insulin use during pregnancy.
Stratified analyses by clinic type (diabetes, obstetric, and other)
Variables were retained in regression models with a P<0.10, and two-way interaction terms (P<0.10) from multivariate models were considered to be evidence of effect modification.
Statistical significance at P<0.05.

Data Collection Summary:

Timing of Measurements

Glycated hemoglobin test at baseline and again at 2 to 4 weeks before the end of pregnancy; all other data collected from prenatal and delivery record

Dependent Variables

Clinic and RD characteristicis: Questionnaire was completed by RDs at the beginning of the study
Biochemical measures: Capillary blood samples were collected from each subject at enrollment and approximately 36 to 38 weeks gestation using a standard finger-prick procedure, and vials were then mailed to a central laboratory for analysis.
Characteristics of pregnant women and birth outcomes: Each subject’s health history, prenatal care, and maternal and infant outcomes data were abstracted from clinic and hospital medical records by RDs using standard forms. A checklist with defined aspects of nutrition assessment and intervention was used to abstract nutrition care data.

Independent Variables

Nutrition practice guidelines group - clinics administered care per GDM nutrition guidelines
Usual care group - clinics administered usual care

Control Variables

Potential confounders (maternal characteristics and duration of nutrition care)
Evaluated effect modification by clinic type (diabetes/endocrinology [diabetes], obstetric/women’s clinics [obstetric], and other hospital or community-based primary care clinics [other]).

Description of Actual Data Sample:

Initial N: 261 women from 25 clinics (range 1 to 22 (mean=8.6) per clinic)

Attrition (final N): 46 lost-to follow up due to no prenatal care after enrollment, transfer to another clinic, unavailable hospital records (final N=215)

Age, y (mean±SD):

Usual Care :30.7±5.8
Practice Guidelines: 31.8±5.6

Ethnicity:

	Usual nutrition care		Practice guidelines nutrition care
Ethnicity (n=204)	n	%	n	%
White	57	71.2	74	60.2
African American	5	6.2	17	13.8
Hispanic	12	15.0	26	21.1
Other	6	7.5	6	4.9

Other relevant demographics:

Education (n=146)
<High school	23	36.5	41	50.0
Some college	23	36.5	11	13.4
College graduate+	17	27.0	30	36.6

Anthropometrics (e.g., were groups same or different on important measures)

Prepregnancy weight (kg) (n=208)	76.9±19.4	76.4±18.2
Height (cm) (n=209)	160.8±7.3	162.7±8.2
BMI (n=205)	29.3±6.5	28.8±6.7
Fasting plasma glucose at GDM diagnosis (mg/dL) (n=192)	97.0±16.9	96.2±14.9
Baseline glycated hemoglobin (n=156)	5.2±0.6	5.0±0.6
Gestational age (wk) at GDM diagnosis (n=179)	28.0±2.9	28.1±2.7
Gestational age (wk) at first nutrition visit (n=213)	29.5±2.6	29.5±2.4
No. of prenatal nutrition visits (n=208)	3.8±2.0	3.5±2.0
Duration in study (wk) (n=215)	8.9±2.9	9.6±2.6

Location: 25 clinics in 20 states in the US

Summary of Results:

Maternal and infant outcomes	Usual nutrition care (n=85) mean±SD or %	Practice guidelines nutrition care (n=130) mean±SD or %	Usual care vs nutrition practice guidelines groups P value
Maternal gestational weight gain (kg)	10.7±5.5	12.9±9.1	0.09
Infant birth weight (g)	3,341±1,004	3,505±901	0.22
Gestational age at birth (weeks)	38.2±3.6	38.7±2.2	0.29
Cesarean section delivery, %	33.7	31.0	0.67
Preterm birth (<37 wks gestation), %	10.6	4.6	0.25
Low birth weight (<2,500 g), %	8.4	2.4	0.27
Macrosomia (>4,000 g), %	13.3	13.4	0.98

^e SD=standard deviation.
^f NA=not available.

Other Findings

Description of Clinics:

~ 60% of usual care and nutrition practice guidelines sites had written protocols for GDM nutrition care before the study.
Diabetes was the primary area of practice for at least half of the RDs in both groups, and they had comparable years of experience working with GDM, but the nutrition practice guidelines sites had more certified diabetes educators than did the usual care sites (78% vs 56%).

Groups and clinic type	Adjusted Mean Birth Weight^a		P value
	Usual care	Nutrition practice guidelines
	←g±SE^b→
Treatment group	3,343±60	3,475±49	0.06
Treatment group by clinic type			0.09
Diabetes/endocrinology	3,402±65	3,411±98
Obstetrics/women’s clinic	2,995±129	3,531±57
Other hospital or community-based clinic	3,631±111	3,484±81

^a Least-square means for infant birth weight adjusted for gestational age, woman’s prepregnancy weight and height, duration of nutrition care, insulin use, and race/ethnicity (n=200).
^b SE=standard error.

Proportion of women in the usual care group had glycated hemoglobin levels that exceeded 6% at follow-up: 13.6% in usual care vs 8.1% practice guidelines group, (P=0.26).
Fewer women in the nutrition practice guidelines group received insulin compared with those in the usual care group (24.6% and 31.7%, respectively) (P=0.05).

Author Conclusion:

The validation of nutrition practice guidelines for GDM demonstrated that provision of evidence-based nutrition practice guidelines to RDs can change practice and result in improved glycemic control and perinatal outcomes. A key finding was that the effect of the guidelines differs according to the clinic type. The impact was greater in obstetric and other clinics compared with diabetes clinics. Although diabetes clinics were no more likely to have written protocols available before the study, most RDs at these sites were certified diabetes educators with advanced diabetes knowledge and skills. Moreover, RDs in diabetes clinics were most likely exposed to previous nutrition practice guidelines developed for type 1 and type 2 diabetes mellitus. As a result, the nutrition practice guidelines reflected nutrition care that was often already being provided by RDs in diabetes clinics.

Funding Source:

Industry:

Splett and Asociates, Kaiser Permanente

Other:

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Trend toward differences in distribution of baseline characteristics and clinic type between groups

Unclear if drop-out was differential between groups

Did compare # of nutrition visits between groups, but did not include other process measures between groups (i.e. % women self-monitoring, completing food records, urine ketones)

Attrition led to inadequate sample size to detect significant differences (per authors needed at 250-276)

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?	No
	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?		???
	4.1.	Were follow-up methods described and the same for all groups?	???
	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%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	???
	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?	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?	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?	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)?	Yes
	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?	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?	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