New Clinical Rec Says Evidence Insufficient to Support Routine Screening for Gestational Diabetes

According to new guidance (scroll down to "Diabetes, Gestational") the AAFP has approved for inclusion in its recommendations for clinical preventive services, insufficient evidence exists to support routine screening for gestational diabetes mellitus.

The Academy based its recommendations on those issued last summer by the U.S. Preventive Services Task Force, or USPSTF. The task force said in its recommendations that there is insufficient evidence to assess the balance between the benefits and harms of screening women for gestational diabetes before or after 24 weeks of gestation.

The USPSTF noted in its recommendations that positive screening results subject women to short-term anxiety and that most positive results actually are false-positives.

Valerie King, M.D., M.P.H., of Portland, Ore., a member of the AAFP Commission on Health of the Public and Science, said the commonly used 50-gram, one-hour glucose challenge test, or GCT, has high specificity and low sensitivity.

"The rest of the world uses a 75-gram test," King said, referring to the test recommended by the World Health Organization. "It's not just a screening test, it's a diagnostic test. A screening test by definition should identify close to all of the people who have the condition."

An abnormal 50-gram GCT result is typically followed by a 100-gram, three-hour oral glucose tolerance test, or OGTT. Two or more abnormal values on the OGTT are considered a diagnosis of diabetes.

King, who is associate professor and director of the Oregon Health & Science University Joint Family Medicine/Public Health and Preventive Medicine Residency in Portland, said most U.S. physicians who provide maternity care screen all pregnant women for gestational diabetes, a standard that has become entrenched in practice despite the lack of evidence to support it.

"Why? Well, why do we do so many things in this country that aren't evidence-based?" King asked. "We do a lot of screening in this country because we're afraid to miss something."

The USPSTF said that until there is better evidence on screening for gestational diabetes, physicians should discuss screening with their patients and make case-by-case decisions. The task force said several groups of women are at increased risk of developing gestational diabetes, such as those who

"The more risk factors they have, the higher the chance that they'll have gestational diabetes, and the higher the chance that a positive test won't be a false-positive," King said.

King said she screens women who have had gestational diabetes in previous pregnancies and talks with other women about the option of being screened.

"You need to have a conversation," she said. "I feel pretty strongly that in the absence of really good evidence for the test, women get to choose whether or not to have the test."

The AAFP also approved two other pregnancy-related items in its recommendations for clinical preventive services: