USPSTF Favors Gestational Diabetes Testing

All asymptomatic pregnant women should be screened for gestational diabetes after 24 weeks’ gestation, according to draft guidelines from the U.S. Preventive Services Task Force (USPSTF).

The common practice of screening before 24 weeks based on risk factors didn’t get either a thumbs up or down, as the group cited insufficient evidence from its literature reviews appearing online in the Annals of Internal Medicine. The same was true for which test and threshold to use for screening.

The task force had previously suggested insufficient evidence for any gestational diabetes screening.

The update aligns most closely with guidelines from the American Diabetes Association, which recommends screening all women without a preexisting diabetes diagnosis at 24- to 28-weeks’ gestation using a 75-g, 2-hour oral glucose tolerance test (OGTT).

The American College of Obstetricians and Gynecologists recommends screening all but low-risk women, although that organization is also in the process of a guideline revision.

The shift for the USPSTF appeared to have hinged on more evidence for a benefit of treating gestational diabetes since the last revision in 2008.

The literature review by Lois Donovan, MD, of the University of Calgary, Alberta, and colleagues indicated that diet modification, glucose monitoring, and insulin when needed resulted in less preeclampsia, shoulder dystocia, and macrosomia.

“When these outcomes are considered collectively, there is a moderate net benefit for both mother and infant,” the draft guideline noted.

Evidence for long-term metabolic benefits for the mother and baby weren’t certain.

But there was little evidence for harm aside from more prenatal visits. Small-for-gestational age and neonatal hypoglycemia weren’t more common with treatment, although the trials may have been underpowered to detect meaningful differences, Donovan’s group cautioned.

The treatment literature review included five randomized, controlled trials and six cohort studies. The group’s review of the literature on screening turned up 51 studies, but that evidence didn’t show a clear winner among the various strategies.

The characteristics of an oral glucose challenge test with a threshold of 7.8 mmol/L (140 mg/dL) to indicate a positive screen were sensitivity of 70% to 88%, specificity of 69% to 89%, a positive likelihood ratio of 2.6 to 6.5, and a negative likelihood ratio of 0.16 to 0.33, the review found.

A lower threshold of 7.2 mmol/L (130 mg/dL) had higher sensitivity of 88% to 99% but lower specificity of 66% to 77%, which yielded a positive likelihood ratio of 2.7 to 4.2 and negative likelihood ratio of 0.02 to 0.14.

Fasting plasma glucose has been suggested as an alternative initial measurement that is easier and less time-consuming to obtain.

A threshold of 4.7 mmol/L (85 mg/dL) on that test had similar sensitivity of 87% but low specificity of 52% and low positive likelihood ratio of 1.8, which “suggests that it is not as good at predicting an abnormal OGTT result,” the authors noted.

Glycated hemoglobin level has also been suggested as an alternative but had poorer test characteristics than the other tests.

The limited evidence on these alternative screening approaches was inadequate, according to the draft guidelines. It didn’t recommend one screening test or threshold as the best for clinical practice.

There were few data on screening tests before 24 weeks’ gestation.

The period for public comment on the draft guidelines ends June 24, after which the final recommendations will be released.

The reviews were funded by the Agency for Healthcare Research and Quality.

Donovan reported a contract with the University of Alberta Evidence Practice Centre for an evidence report on screening and diagnosis of gestational diabetes, and grant funds from International Diabetes Federation and Eli Lilly.

Primary source: Annals of Internal Medicine
Source reference:
Donovan L, et al “Screening tests for gestational diabetes: A systematic review for the U.S. Preventive Services Task Force” Ann Intern Med 2013; 159.

Additional source: Annals of Internal Medicine
Source reference:
Hartling L, et al “Benefits and harms of treating gestational diabetes mellitus: A systematic review and meta-analysis for the U.S. Preventive Services Task Force and the National Institutes of Health Office of Medical Applications of Research” Ann Intern Med 2013;159.

Add Your Knowledge ™

Register Today

Earn Free CME Credits by reading the latest medical news
in your specialty.

Sign Up

Crystal Phend

Staff Writer

Crystal Phend joined MedPage Today in 2006 after roaming conference halls for publications including The Medical Post, Oncology Times, Doctor’s Guide, and the journal IDrugs. When not covering medical meetings, she writes from Silicon Valley, just south of the San Francisco fog.