New Criteria for Gestational Diabetes Increase Diagnoses

Kate Johnson

December 05, 2011

December 5, 2011 (Dubai, United Arab Emirates) — The use of more stringent criteria for diagnosing gestational diabetes mellitus (GDM) is associated with a 137% increase in prevalence, according to an Italian study presented here at the International Diabetes Federation World Diabetes Congress 2011.

The new criteria, proposed by the International Association of Diabetes and Pregnancy Study Groups (IADPSG) and adopted recently in Italy, have been endorsed by the American Diabetes Association but not by the American College of Obstetricians and Gynecologists.

The new criteria call for the diagnosis of GDM after a single abnormal fasting plasma glucose measurement of 92 to 126 mg/dL at the first prenatal visit or, if the initial test is normal, an abnormal oral glucose tolerance test at 24 to 28 weeks of gestation. If the fasting plasma glucose is 92 mg/dL or greater, GDM is diagnosed when the 1-hour value is 180 mg/dL or greater or when the 2-hour value is 153 mg/dL or greater.

The researchers, led by Emilia Lacaria, from the University of Pisa in Italy, analyzed 660 pregnant women who were being evaluated for GDM using the new criteria, and compared them with a historic cohort that had been evaluated using the old Carpenter–Coustan criteria.

The mean age of the women was 33 years, 18.5% had a family history of diabetes, and 58% were primiparous.

Early diagnosis of GDM was made in 18 women; the other 642 women underwent an oral glucose tolerance test, which yielded a diagnosis of GDM in another 118 women and normal glucose tolerance in the rest (79.4%).

In total, 136 (20.6%) women were diagnosed with GDM — 13.2% after early evaluation and 88.8% after an oral glucose tolerance test.

When the researchers compared their cohort with a historic cohort of 3950 women diagnosed using the older criteria (Diabetes Res Clin Pract. 2003;62:131-137), the new criteria were associated with a 136.8% increase in prevalence (20.6% vs 8.7%).

After analyzing the data from the old study and including all subjects (6.7%) classified as having impaired glucose tolerance in the GDM group, the difference was less apparent (20.6% vs 15.4%), but a 34% difference still remained.

The dramatic increase in GDM diagnosis seen with the proposed IADPSG criteria have been the subject of much discussion, but it is important to remember that using old data as a comparator is inherently flawed, said Boyd Metzger, MD, from Northwestern University Feinberg School of Medicine in Chicago, Illinois, who chaired the session and was a member of the IADPSG guidelines writing group.

"There's been a continuous rise in overweight and obesity around the globe, and there are several papers showing that when using exactly the same standardized approach, the incidence of GDM has gone up 40% to 50%," he said in an interview with Medscape Medical News. "There's been a continuously moving background, so it's very hard retrospectively to compare."

Dr. Metzger maintains that the marked increase in diagnosis of GDM with the new criteria is due to the fact that now only 1 abnormal test is required. Previous criteria required 2 abnormal oral glucose tolerance tests.

"There have been dozens of papers written in the past 20 years pointing out that people who had 1 abnormal test value and who were called "normal" had a lot of the outcomes that are similar to those who were diagnosed."

He explained that many diabetes experts in the United States are waiting for next year's National Institutes of Health consensus conference on diagnosing GDM to make their decision about the new criteria. The World Health Organization is expected to announce its position before that time.

The study authors and Dr. Metzger have disclosed no relevant financial relationships.

International Diabetes Federation (IDF) World Diabetes Congress 2011: Abstract O-0393. Presented December 4, 2011.

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