Draft Research Plan
Gestational Diabetes Mellitus: Screening
February 28, 2019
Recommendations made by the USPSTF are independent of the U.S. government. They should not be construed as an official position of the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.
* No assumptions will be made about whether hyperglycemia first discovered early in pregnancy (e.g., the first trimester) is GDM or some other form of diabetes; the term “GDM” will include all women who have hyperglycemia but do not meet criteria for overt diabetes at any time point during pregnancy.
† Using two-step (screening and, when indicated, diagnostic testing) or one-step (diagnostic testing only) screening strategies, each based on various criteria and thresholds, and offering treatment to women diagnosed with GDM.
‡ Harms from screening or diagnosis include, but are not limited to, adverse effects of screening tests (e.g., vomiting); anxiety or depression for the mother from screening tests or a GDM diagnosis; and consequences of labeling for the mother, fetus, or newborn (e.g., unnecessary delivery interventions, additional interventions with formula, or separation of newborn and mother).
§ Harms from treatment include severe maternal or fetal/neonatal hypoglycemia and delivery of small for gestational age newborns.
Abbreviations: GDM = gestational diabetes mellitus; IGT = impaired glucose tolerance; KQ = key question; LGA = large for gestational age; NICU = neonatal intensive care unit; T2DM = type 2 diabetes mellitus.
1 a. Does screening for gestational diabetes mellitus (GDM) reduce poor maternal, fetal/neonatal, and childhood health outcomes?
b. Does screening for GDM reduce poor maternal, fetal/neonatal, and childhood intermediate outcomes?
c. Does the effectiveness of screening for GDM differ for subpopulations defined by timing during pregnancy, body mass index (BMI), age, or ethnicity/race?
2. What are the harms of screening for GDM to the mother, fetus, or newborn?
3 a. What is the comparative effectiveness of different screening, diagnostic, or combined strategies for maternal, fetal/neonatal, and childhood health outcomes?
b. What is the comparative effectiveness of different screening, diagnostic, or combined strategies for maternal, fetal/neonatal, and childhood intermediate outcomes?
c. Does the comparative effectiveness of different screening strategies differ for subpopulations defined by timing during pregnancy, BMI, age, or ethnicity/race?
4 a. What is the diagnostic accuracy of commonly used screening tests for GDM?
b. Does the accuracy of these screening tests differ for subpopulations defined by timing during pregnancy, BMI, ethnicity/race, or prevalence of GDM?
5. What is the association between a diagnosis of GDM and outcomes in women meeting lower versus higher diagnostic thresholds?
6 a. Does treatment of GDM reduce poor maternal, fetal/neonatal, and childhood health outcomes?
b. Does treatment of GDM reduce poor maternal, fetal/neonatal, and childhood intermediate outcomes?
c. Does the effectiveness of treatment of GDM differ for subpopulations defined by timing during pregnancy, diagnostic criteria, BMI, age, or ethnicity/race?
7. What are the harms of treatment of GDM, including severe maternal and fetal/neonatal hypoglycemia and delivery of small for gestational age newborns?
Contextual questions will not be systematically reviewed and are not shown in the Analytic Framework.
- What is the association between measures of blood glucose (e.g., fasting and postload glucose concentration, percent hemoglobin A1c) and outcomes, and does it differ based on timing of diagnosis?
- What is the association between GDM diagnosis before 24 weeks of gestation and outcomes, and does it differ based on timing of diagnosis?
- How strongly do intermediate outcomes predict long-term or health outcomes in women who have had GDM or their children?
- Are postpartum interventions effective for reducing the incidence of long-term and health outcomes in women previously diagnosed with GDM, their children, or both?
The Proposed Research Approach identifies the study characteristics and criteria that the Evidence-based Practice Center will use to search for publications and to determine whether identified studies should be included or excluded from the Evidence Review. Criteria are overarching as well as specific to each of the key questions (KQs).
|Population||KQs 1–5: Pregnant women with no known history of pre-existing diabetes mellitus
KQs 6, 7: Pregnant women with GDM or hyperglycemiaKQs 1c, 3c, 6c: Subpopulations defined by pre-pregnancy BMI (i.e., <25 vs. ≥25 kg/m2, <30 vs. ≥30 kg/m2), age (<25 vs. ≥25 years, <35 vs. ≥35 years), timing during pregnancy, ethnicity/race (i.e., white vs. nonwhite), and severity of hyperglycemia (KQ 6c only)
|Populations in which ≥20% have pre-existing diabetes mellitus|
|Interventions/ Exposure||KQs 1–3: Screening using two- or one-step strategies* followed by treatment of women diagnosed with GDM. In two-step strategies, the screening test must be FPG, 50-g OGCT, risk-based method (clinical or historical using ≥1 factors), or hemoglobin A1c; in one- and two-step strategies, the diagnostic test must be FPG or OGTT.
KQ 4: Screening tests (i.e., FPG, 50-g OGCT, risk-based method, or hemoglobin A1c).
KQ 5: Diagnosis of GDM but no treatment (e.g., criteria at lower threshold than that used by study site for initiating treatment).KQs 6, 7: Any treatment for GDM, including, but not limited, to dietary advice, blood glucose monitoring, insulin therapy (all preparations), glucose-lowering medications, and combinations thereof.
|KQs 1–5: Alternative methods to delivering glucose (e.g., candy bars).|
|Comparators||KQs 1, 2: No screening
KQ 3: Another screening strategy (i.e., one- vs. two-step screening, different diagnostic criteria and/or cut-offs, different timing in pregnancy, selective/risk-based vs. universal screening)
KQ 4: Any FPG or OGTT used for diagnosis of GDM
KQ 5: No GDM by any criteria applied in the studyKQs 6, 7: No treatment (i.e., no additional management or minimally active intervention, such as printed materials)
|KQs 1–5: Different methods to delivering glucose (e.g., candy bars, glucose loads) with same diagnostic criteria
KQs 6, 7: All active interventions
|Outcomes||KQs 1, 3, 5, 6:
KQ 2: Adverse effects of screening tests (e.g., vomiting), anxiety or depression for the mother from screening tests or diagnosis, and consequences of labeling for the woman, fetus, or newborn (e.g., unnecessary delivery interventions, additional interventions with formula, separation of newborn and mother, breastfeeding challenges/failure)
KQ 4: Sensitivity, specificity, predictive values, accuracy, and yield (i.e., prevalence)
KQ 7: Severe maternal or neonatal hypoglycemia, delivery of small for gestational age newborns
|KQs 1, 3–6: Other outcomes|
|Outcome assessment timing||Any duration of followup|
|Setting||KQs 1–3, 5–7: Settings applicable to primary care; countries not categorized as “Very High” on the Human Development Index (as defined by the United Nations Development Programme) will be subject to sensitivity analysis
KQ 4: Any setting
|Study designs||KQs 1, 2: RCTs, CCTs, and controlled observational studies
KQ 2: Studies in which all participants are screened but harms are assessed before (i.e., earlier in pregnancy) and after screening
KQ 3: RCTs and CCTs
KQ 4: Prospective cohort studies and single arms of trials
KQ 5: Observational studies and single-arm trials (i.e., arms not receiving treatment)KQs 6, 7: RCTs, CCTs; controlled observational studies if no trials exist
|Systematic reviews,** abstracts, and conference proceedings|
* Two-step screening involves a screening test (e.g., 50-g OGCT) followed by a diagnostic test (i.e., OGTT), whereas one-step screening involves one test used for diagnosis in everyone.
** Systematic reviews, identified from a preliminary search for reviews on GDM and from searches for primary studies, will be scanned for potentially relevant studies but will not be included as the unit of analysis.
Abbreviations: BMI = body mass index; CCT = controlled clinical trial; FPG = fasting plasma glucose; GDM = gestational diabetes mellitus; IGT = impaired glucose tolerance; KQ = key question; OGCT = oral glucose challenge test; OGTT =oral glucose tolerance test; RCT = randomized, controlled trial.