SAN FRANCISCO – Updated guidelines from the American Diabetes Association open the door to using a two-step approach to gestational diabetes screening.
Screening is still recommended for undiagnosed type 2 diabetes at the first prenatal visit in those with risk factors, and for gestational diabetes mellitus (GDM) between weeks 24 and 28 of gestation.
What’s changed in the 2014 Standards of Medical Care in Diabetes (Diabetes Care 2014;37(suppl 1):S14-80) is how that screening is accomplished, Dr. Richard W. Grant, chair of the ADA professional practice committee, said at the annual advanced postgraduate course held by the American Diabetes Association.
In prior years, the ADA adopted the International Association of Diabetes and Pregnancy Study Groups (IADPSG) 2009 recommendation that a 2-hour, 75-gram oral glucose tolerance test (OGTT) be performed the morning after a fast of at least an 8 hours.
A two-step approach was added this year to reflect the 2013 National Institutes of Health Consensus Guidelines recommendation for a 1-hour, 50-gram glucose tolerance screening test followed by a fasting OGTT on another day, if the test is abnormal.
One-step vs. two-step approach
"The issues for these two approaches are the sensitivity with which you can diagnose GDM and the difficulty in implementing these two approaches," said Dr. Grant, a research scientist with Kaiser Permanente Northern California, Oakland.
The one-step approach tends to be more sensitive and diagnoses a broader range of GDM, but it may be a barrier to screening because it requires the patient to fast for 8 hours, he said. Though the one-step approach allows for a diagnosis of GDM within the context of a single office visit, critics also argue its tight diagnostic glucose cut points could dramatically increase the prevalence of GDM from about 5%-6% to 15%-20%, and bring added health care costs and interventions without clear evidence of improved outcomes.
Dr. Richard W. Grant
On the other hand, the two-step approach may be more palatable to women because it avoids the up-front fasting requirement, but it could miss GDM in women with an abnormal screen who fail to return for a second visit.
"The bottom line is we need to make sure we do gestational diabetes screening, whichever method we use," Dr. Grant said. "What’s more important is that all women in early pregnancy get screened."
During a discussion following the presentation, a Canadian attendee said similar recommendations released last fall in Canada allowing two screening methods, albeit with different diagnostic thresholds, have resulted in confusion, particularly among referring obstetricians and endocrinologists.
Dr. Grant said there shouldn’t be confusion surrounding the new option as long as recommendations are consistent within an institution.
"I don’t think it’s actually going to make people change what they’re doing currently," he said in an interview. "There’s not a good reason to jump from one to another if you’ve already chosen an approach."
In a separate interview, Dr. R. Harsha Rao, with the Center for Diabetes and Endocrinology at the University of Pittsburgh, said he can see the rationale for the one-step method, but that the two-step approach is almost implanted in the DNA of American obstetricians and that this behavior pattern will be difficult to change for practical reasons alone.
"Patients don’t like 75 grams of Glucola; it’s an awful-tasting substance," he said. "I’ve had patients tell me they felt like [vomiting] when they got the 75-gram Glucola load, and as it is, ‘I’m pregnant and already feeling nauseated.’ "
In addition, there’s the added stress of waiting for a second appointment and a definitive diagnosis for women who screen positive.
The ADA’s bimodal approach to gestational screening reflects an overarching theme of individualized care for diabetes in the 2014 standards. The guidelines are updated annually and this year they contain 232 recommendations, of which 52% are based on high level A or B evidence.
Individualized diabetes care
"One of the themes that comes out in looking at the data very carefully is that you can’t have a one-size-fits-all approach," Dr. Grant observed.
To that end, the guidelines maintain an earlier recommendation raising the systolic blood pressure target goal for hypertension to 140 mm Hg, but also allow a target goal of less than 130 mm Hg in certain populations, such as younger patients.
Dr. Grant observed that the ADA’s position was confirmed by the U.S. Preventive Services Task Force’s recent endorsement of GDM screening using the two-step approach.
"The USPSTF said that the two-step method is an accurate approach, which is what the ADA also says," he remarked.
Based on the recently revised 2013 ADA nutrition position paper (described in the next section below), the guidelines also encourage individualized dietary approaches rather recommending one particular diet over another, Dr. Grant said.