An independent panel convened March 4–6 by the National Institutes of Health (NIH) concluded that despite "certain operational advantages" to a new one-step strategy for diagnosing gestational diabetes mellitus (GDM), more evidence is needed to understand the harms and benefits of this approach. The 15-member panel therefore recommended adhering to the two-step approach commonly used by obstetrical practices in the U.S. This approach, also endorsed by the American College of Obstetricians and Gynecologists in 2011, involves a 50-gram, 1-hour screening test followed by a 3-hour glucose tolerance test for patients with results ≥140 mg/dL on the screening test or glucose levels >130 mg/dL.
The panel's recommendations are at odds with those of the American Diabetes Association, the International Association of Diabetes and Pregnancy Study Groups, and the National Academy of Clinical Biochemistry, all of which have endorsed a single 75-gram oral glucose tolerance test for all pregnant women between 24–28 weeks' gestation not previously known to have diabetes. These recommendations were based on findings from the landmark Hyperglycemia and Adverse Pregnancy Outcome study of approximately 25,000 pregnant women that demonstrated a strong, graded relationship between maternal glycemia and adverse pregnancy outcomes (CLN 2010 May;36:5).
The NIH panel's chair, Peter VanDorsten, MD, stated in a news conference at the conclusion of the group's 3-day deliberation that the panel recognized the benefits of having "a consistent diagnostic standard across one's lifespan and better comparability of research outcomes globally." However, the panel seemed particularly troubled that the new approach could increase the prevalence of GDM over current levels by two-to-three fold, from an estimated 5–6% of pregnant women in the U.S. to as many as 20%. "The labeling of these women may have unintended consequences such as an increase in life disruptions, anxiety, increased clinic visits, and more intensive antenatal and newborn assessments. Moreover, the care of these women will generate additional direct and indirect healthcare costs," he explained. VanDorsten is Lawrence L. Hester, Jr. professor of obstetrics and gynecology at the Medical University of South Carolina in Charleston.
The panel called for more cost-benefit and cost-effectiveness research to understand how changing current diagnostic standards might impact patients, providers, and the healthcare system. The panel considered the results of a systematic literature review prepared under contract to the U.S. Agency for Healthcare Research and Quality as well as presentations from experts in the field. NIH convened the group as part of its consensus development program, which is designed to address controversial questions of public health importance when there may be discordance between clinical practice and available evidence. The panel sought to answer seven questions, including what are the current screening and diagnostic methodologies and thresholds for GDM, what are the effects of these approaches for patients, providers, and the healthcare system, and what are key research gaps around diagnosing GDM.
The panel particularly cited insufficient evidence clearly demonstrating improved short- and long-term outcomes from a one-step approach. "We understand that operationally it makes sense to get in line with what's being done in the rest of the world … but we don't feel like there are robust enough data now that extending the diagnosis outweighs the potential harms," said VanDorsten. "So we've absolutely left the door ajar for reconsideration should these data be forthcoming."