Transforming postpartum diabetes screening with new glucose tolerance test

New research suggests that a shorter, one-hour glucose tolerance test outperforms the standard two-hour test in predicting future risk of postpartum diabetes and could transform clinical practice.

Pregnancy acts as a stress test that can indicate a woman’s predisposition to type 2 diabetes, as the increased demands on the body can reveal underlying limitations in their capacity to produce enough insulin for blood sugar control.

Women with gestational diabetes are seven to ten times more likely to develop diabetes later, making postpartum testing crucial. However, only about half of these women return for their glucose tests.

The gold standard two-hour Oral Glucose Tolerance Test (OGTT) requires women to fast overnight and then complete the test the next morning, at which time blood is drawn for measurement of their blood sugar, followed by consumption of a sugar drink, and then waiting for two hours for repeat blood sugar measurement.

Recognising the issue, the International Diabetes Federation last year recommended shortening the test duration to one hour, citing evidence that this timeframe is not only more practical but also more sensitive.

Research has shown that the one-hour test captures the peak blood sugar levels. If the blood sugar level is high at this point, it suggests that the body is not processing glucose efficiently, identifying an elevated risk of developing diabetes.

“Gestational diabetes provides a unique opportunity to identify a very high risk of a major future illness at a young age, “ said study lead Dr. Retnakaran, clinician scientist at the Lunenfeld-Tanenbaum Research Institut and professor at the University of Toronto.

“It is for this reason that, after having gestational diabetes, it is recommended that women do an oral glucose tolerance test within six months of delivery.

“But the reality is that many women don’t come back to do this test. The first six months postpartum are hectic, and finding time for a two-hour test is challenging.”

The study compared the predictive capabilities of the one-hour and two-hour tests at three months postpartum for pre-diabetes status at five years postpartum among 369 women. The one-hour test not only matched the two-hour test but was even a stronger predictor of pre-diabetes status five years later.

This suggests that the one-hour OGTT could improve completion rates of testing after pregnancy and facilitate early intervention, potentially revolutionising diabetes prevention for postpartum women.

“If you identify an individual who has risk of diabetes, one of the most effective interventions for reducing this risk is helping them to lose weight. And we are at a point in time where weight loss has never been more achievable for large numbers of people thanks to new medications that are now available,” said Dr. Retnakaran.

As a next step, Dr. Retnakaran plans to conduct a clinical trial to confirm if the one-hour test can indeed increase compliance before it can become standard practice.