Diagnosing Gestational Diabetes a 2-Step Process, Says Panel

Miriam E. Tucker

March 08, 2013

Diagnosing gestational diabetes should remain a 2-step approach, a panel convened by the National Institutes of Health has decided.

The independent 15-member panel advised that, despite several advantages of 1-step approaches and their widespread use outside the United States, more research is needed before any changes should be made to the 2-step diagnostic approach that is the current US standard.

"Despite potential benefits, there are several concerns about the 1-step approach," panel chair Peter VanDorsten, MD, from the Medical University of South Carolina, Charleston, told reporters attending a telebriefing. "There's much debate regarding the choice of test and the tradeoffs of each approach."

He pointed out the 1-step approach is anticipated to increase the frequency of diagnosis 2 to 3-fold.

Other panel members included specialists in maternal-fetal medicine, obstetrics and gynecology, endocrinology and infertility, pediatrics, nutrition, epidemiology, economics and statistics. There was also a patient representative from the American Diabetes Association.

The statement, issued as a draft, is expected to be finalized within 6 weeks.

1 Step Versus 2

Currently, the diagnostic approach used by most obstetricians in the US — and endorsed by the American College of Obstetricians and Gynecologists (ACOG) — involves an unfasted 1-hour, 50-gram glucose challenge followed by a diagnostic fasted 3-hour, 100 gram oral glucose tolerance test for women who exceed a designated glucose cutoff.

Using this approach, approximately 5% of pregnant women are diagnosed with gestational diabetes mellitus totalling about 240,000 annual births in the US.

The 1-step approach, proposed by the World Health Organization (WHO) and the International Association of Diabetes and Pregnancy Study Groups (IADPSG) and supported by the American Diabetes Association (ADA), involve a single 75 gram oral glucose fasted challenge followed by 2 hours of testing.

Use of a single-step diagnostic test in the US would increase the proportion of pregnancies diagnosed with gestational diabetes to at least 15%.

What's not clear, Dr. VanDorsten said, is whether those additional women would benefit from having the diagnosis. "We need information from the so-called real world as to the impact this is having on patients, on obstetrical, and fetal and neonatal outcomes before subjecting many more women to the impact of a diagnosis of gestational diabetes."

Among the advantages considered by the panel, the single-step process would bring consistency between the US and the rest of the world. It would also allow for a uniform standard of diabetes diagnosis in general since a single 75-gram oral glucose tolerance test is used to diagnose diabetes in the non-pregnant population. And, it would allow for a diagnosis in just 1 visit rather than 2.

However, the panel identified numerous potential downsides including the increased cost, estimated by one study to increase from $636 million to $2 billion. Other potential negatives included increased anxiety for women, possible adverse effects of treatment such as hypoglycemia, and increased use of cesarean delivery.

Dr. VanDorsten said that while there is considerable evidence showing improved pregnancy outcomes for women who are diagnosed with a 2-step method and subsequently treated, such data are not available yet for 1-step approaches.

"Until we get that information, we felt it premature to exact these increased challenges to the healthcare system, the healthcare providers, and more importantly, the patients themselves," he said.

The consensus panel provided a list of research needs including a randomized controlled trial comparing outcomes of the 2 approaches, a cost-benefit analysis, and an exploration of the psychological impact of a diagnosis.

Reaction

In a statement provided to Medscape Medical News, ACOG said the organization "agrees with the conclusions of the NIH panel that before testing is changed and diagnostic criteria expanded to assign this diagnosis to 2 or 3 times more patients, the real-world implications of such changes should be carefully studied."

Such studies, the society said, should examine whether proposed changes improve the health of mothers and babies. "Also, any changes must be balanced against the resources required to implement them. ACOG encourages providers to continue following the current recommendations using a 2-step approach with previously established glucose thresholds to screen for and diagnose gestational diabetes."

In contrast, ADA chief scientific and medical officer Robert Ratner told Medscape Medical News, “We are disappointed that the NIH review panel chose to return to a cumbersome 2-step screening program to identify gestational diabetes for what appear to be economic reasons."

Dr. Ratner said that use of a 1-step diagnostic approach is supported by data from the landmark Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study, which found an increased risk for adverse pregnancy and neonatal outcomes even at mild levels of maternal hyperglycemia.

"We define gestational diabetes mellitus based upon the risk to the fetus and newborn of maternal hyperglycemia. The HAPO Study definitively demonstrated these risks to be linear with the increase in maternal glucose concentrations based upon a single glucose tolerance test. The new recommendations appear to ignore or minimize this study of over 25,000 pregnancies."

Regarding the concern about the greater numbers of women who would be diagnosed with gestational diabetes based on the 1-step method, Dr. Ratner said, "If these criteria are based on increasing risk to the fetus/newborn, isn't it more appropriate to recognize the risk rather than ignore it? We do our patients a disservice by denying conditions that increase morbidity and are potentially remediable."

Dr. VanDorsten said that this new consensus statement is not the last word. "We don't feel the data are robust enough now…but we have absolutely left the door ajar for reconsideration should these data be forthcoming."

The Consensus Development Conference is sponsored by the National Institutes of Health Office of Disease Prevention and the Eunice Kennedy Shriver National Institute of Child Health and Human Development, along with other NIH and U.S. Department of Health and Human Services components. Panel members were paid for travel expenses, but received no other compensation for participation. Dr. Ratner is employed by the American Diabetes Association and has no other disclosures.

The National Institutes of Health Consensus Development Program: Diagnosing Gestational Diabetes Mellitus Conference. Presented March 6, 2013.

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