Lack of Evidence for routine screening for Gestational Diabetes

by faithgibson on October 8, 2012

Guidelines Issued About Lack of Evidence for Screening for Gestational Diabetes

Article reposted fron Medscape, May 23, 2008 – Excerpts

The US Preventive Services Task Force (USPSTF) has issued a recommendation statement and systematic review about lack of evidence to recommend screening for gestational diabetes mellitus (GDM) .. published May 20 issue of the Annals of Internal Medicine.

“In 2003, the U.S. Preventive Services Task Force concluded that evidence was insufficient to advise for or against routinely screening all pregnant women for [GDM],” write Teresa A. Hillier, MD, MS, from Kaiser Permanente Northwest in Portland, Oregon, and colleagues from the USPSTF who coauthored the systematic review of evidence about the benefits and harms of screening for gestational diabetes.

The USPSTF searched MEDLINE, Database of Abstracts of Reviews of Effects, Health Technology Assessment Database, National Institute for Health and Clinical Effectiveness, and Cochrane Library for reports published from January 2000 to November 15, 2007.

They also searched these databases from 1966 to 1999 for additional studies on screening at fewer than 24 weeks’ gestation, as well as citations in the 2003 evidence report and studies identified by consulting experts and searching bibliographies.

Inclusion criteria for the literature review were English-language studies using standard 1- or 2-step testing for GDM and determining 1 or more of the following end points:

  • neonatal mortality
  • brachial plexus injury
  • clavicular fracture
  • admission to a neonatal intensive care unit (ICU) for hypoglycemia
  • hyperbilirubinemia
  • respiratory distress syndrome (RDS)
  • maternal mortality
  • preeclampsia or pregnancy-induced hypertension

The five key questions guiding this systematic review were:

  • Is screening for GDM associated with a reduction in perinatal morbidity and mortality for mother or infant after 24 weeks’ gestation and/or during the first trimester and up to 24 weeks’ gestation?
  • For currently available screening tests for GDM, what are the sensitivities, specificities, reliabilities, and yields after 24 weeks’ gestation, during the first trimester, and up to 24 weeks’ gestation?
  • Is treatment of GDM after 24 weeks’ gestation and during the first trimester and up to 24 weeks’ gestation associated with lower perinatal morbidity and infant or maternal mortality?
  • Is screening for GDM associated with adverse effects?
  • Is treatment of GDM associated with adverse effects?

Two reviewers assessed 1607 abstracts, critically evaluated 288 articles, and qualitatively synthesized 13 studies.

There were no randomized controlled trials (RCTs) identified that directly determined the benefits and harms of screening for GDM. However, 1 good-quality RCT of treatment of mild GDM in a population detected by screening suggested that treatment of GDM was associated with lower risk for gestational hypertension and for serious neonatal complications.

Evidence was very limited regarding the value of early screening for GDM (before 24 weeks’ gestation). Limited evidence supports the rarity of serious maternal hypoglycemia in treated women and suggests that overall quality of life is not worse [editor’s note: what does this mean?] in women treated for GDM compared with that of women not receiving treatment.

A limitation of this review is that the literature is limited by lack of a consistent standard for screening or for diagnosis of gestational diabetes.

“Limited evidence suggests that gestational diabetes treatment after 24 weeks improves some maternal and neonatal outcomes,” the review authors write. “Evidence is even more sparse for screening before 24 weeks’ gestation.”

This review was conducted by the Oregon Evidence-Based Practice Center under contract to the Agency for Healthcare Research and Quality. The authors have disclosed no relevant financial relationships.

The accompanying USPSTF recommendation statement, which is an update of their 2003 recommendation about screening for GDM, was issued after weighing the evidence on the potential maternal and neonatal benefits and physical and psychological harms of screening.

Harms of screening include short-term anxiety in some women with positive screening results and inconvenience to many women and medical practices because most positive screening test results are probably false positives.

The authors note that women at increased risk for GDM are those who are obese, are older than 25 years, have a family history of diabetes, have a history of GDM, or are of Hispanic, American Indian, Asian, or black ethnicity.

Most screening is conducted between 24 and 28 weeks’ gestation, most commonly with an initial 50-g, 1-hour glucose challenge test. If this test is abnormal, a 100-g, 3-hour oral glucose tolerance test (GTT) is performed; 2 or more abnormalities on that test constitute a diagnosis of GDM.

“Current evidence is insufficient to assess the balance of benefits and harms of screening for gestational diabetes mellitus, either before or after 24 weeks’ gestation,” the statement concludes. “Until there is better evidence, clinicians should discuss screening for GDM with their patients and make case-by-case decisions. The discussion should include information about the uncertain benefits and harms as well as the frequency and uncertain meaning of a positive screening test result.”

The authors have disclosed no relevant financial relationships.

Ann Intern Med. 2008;148:759-765, 766-775.

CLINICAL CONTEXT

GDM, defined as glucose intolerance first detected during pregnancy, has been increasing in US women of childbearing age, along with obesity and diabetes mellitus. The American Diabetes Association, the American College of Obstetricians and Gynecologists, and the World Health Organization currently recommend both GDM screening in most pregnant women between 24 and 28 weeks’ gestation and screening high-risk pregnant women at the first antenatal visit.

However, USPSTF concluded in 2003 that evidence was insufficient to advise for or against routinely screening all pregnant women. Fair-to-good evidence showed reduction in fetal macrosomia when screening led to treatment of GDM, but evidence for other health benefits in mothers or infants was insufficient. The USPSTF therefore updated their literature review on this topic and issued an updated position statement on the value of screening for GDM.

PEARLS FOR PRACTICE

  • There are no RCTs directly determining the benefits and harms of GDM screening, but 1 good-quality RCT suggests that treatment of GDM reduces risk for gestational hypertension and for serious neonatal complications.
  • The USPSTF concluded that current evidence is insufficient to evaluate the balance of benefits and harms of screening for GDM, either before or after 24 weeks’ gestation. While awaiting better evidence, clinicians should discuss GDM screening with their patients and make case-by-case decisions, considering the uncertain benefits and harms and the frequency and uncertain meaning of a positive screening test result.

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