Loading ...

A 1-hour postpartum oral glucose tolerance test (OGTT) outperformed the standard 2-hour test for predicting future dysglycemia in women with and without a history of gestational diabetes, according to a new study.

A comparison of the predictive values of both tests, performed at 3 months post partum, showed that the shorter test was superior at predicting the development of prediabetes or diabetes during the subsequent 5 years.

The findings support the adoption of the 1-hour test “as a more convenient option that potentially may increase adherence to the testing,” wrote lead author Ravi Retnakaran, MD, an endocrinologist at Mount Sinai Hospital and clinician scientist at the Lunenfeld-Tanenbaum Research Institute in Toronto, and coauthors.

The data were published on March 3 in Diabetes Care. 

‘Long-Standing Care Gap’

The International Diabetes Federation recently endorsed the 1-hour test in the general population for its convenience, but not specifically in the postpartum population, “presumably because of the absence of evidence for such a statement in that clinical setting,” Retnakaran told Medscape Medical News. “To our knowledge, there were no previous studies comparing 1-hour blood glucose to 2-hour blood glucose for postpartum reclassification and prediction of future prediabetes or diabetes before the current study.”

Women with hyperglycemia in pregnancy are currently advised to undergo the 2-hour OGTT within 6 months after delivery because they are 7-10 times more likely to develop future diabetes than pregnant women without gestational diabetes, explained Retnakaran, who is also a professor at the University of Toronto’s Temerty Faculty of Medicine, Toronto.

In clinical practice, however, about half of this population returns for testing, partly because the 2-hour test is time-consuming and inconvenient for new mothers. Patients also have uncertainty about which provider (eg, obstetrician, endocrinologist, or family physician) is responsible for ordering the test.

The study findings “may provide a strategy for addressing the long-standing care gap in clinical medicine,” said Retnakaran, adding that this gap “is underscored by the rising incidence of gestational diabetes and the recent emergence of interventions (both lifestyle and pharmacologic) that can induce weight loss and thereby modify risk for developing type 2 diabetes.”

Higher Sensitivity

The study was part of a prospective, observational cohort program at a single institution involving all pregnant women across the full spectrum of glucose tolerance. After delivery, women returned for metabolic characterization, including the 1- and 2-hour OGTT at 3 months and 1 year post partum. At 1 year post partum, 471 patients were recruited into the study cohort for further testing at 3 and 5 years. Overall, 369 patients completed all testing.

In their analysis of this population, which included 135 patients with gestational diabetes, the researchers showed that the 1-hour OGTT measured at 3 months identified dysglycemia in almost all patients who were diagnosed by the 2-hour OGTT, in addition to identifying 96 more cases. Specifically, the 1-hour OGTT identified 156 women with dysglycemia, while the 2-hour OGTT identified 70, 60 of whom met 1-hour criteria as well.

The higher sensitivity of the 1-hour test persisted at each timepoint. At 1 year, 68 women with dysglycemia were identified by 1-hour OGTT alone, 13 by 2-hour OGTT alone, and 42 by both tests. At 3 years, 63 women with dysglycemia were identified by 1-hour OGTT, 16 by 2-hour OGTT, and 58 by both tests. And at 5 years, 48 women with dysglycemia were identified by 1-hour OGTT alone, 12 by 2-hour OGTT alone, and 76 women by both.

Regression analyses adjusted for clinical risk factors for diabetes (ie, age, ethnicity, family history of diabetes, body mass index [BMI] at 3 months, and duration of breastfeeding) revealed that on the OGTT at 3 months post partum, the 1-hour glucose value was a stronger predictor than the 2-hour value of subsequent dysglycemia over the next 5 years.

Based on its effect on the concordance index (CCI) of the models, the best predictor of future dysglycemia was the 1-hour OGTT (change in CCI, 16.1%), followed by the 2-hour OGTT (14.9%), non-White ethnicity (6.7%), fasting glucose (5.2%), and BMI (3.2%).

Retnakaran plans to conduct a clinical trial to investigate whether the 1-hour test increases compliance.

Promising Results

Commenting on the findings for Medscape Medical News, Liran Hiersch, MD, head of Maternal-Fetal Medicine at Lis Maternity and Women’s Hospital in Tel Aviv, Israel, said, “As maternal-fetal medicine specialists, we always see pregnancy as a window of opportunity for promoting health and preventive medicine for women. Thus, it is crucial that we encourage women to perform the postpartum OGTT so we can better understand their future risk of dysglycemia and diabetes.” Hiersch was not involved in the research.

“However, we always need to think about how to make this test easier and more appealing for those who have just recently delivered and may have other priorities in mind,” he added. “The results of this study are promising, as the 1-hour OGTT results were found to be superior to the standard 2-hour test.”

Hiersch pointed out that in this study, the 1-hour test identified almost half of the population as at risk for future dysglycemia, “which is less likely and suggests that future prediction models should be developed, using other factors, for a more specific risk calculation.”

The study was funded by the Canadian Institutes of Health Research. Retnakaran and Hiersch reported no relevant financial relationships.

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.