Obese children, who are at increased risk for prediabetes and type 2 diabetes, may not be getting the most appropriate test to screen for these conditions, according to a new Canadian study.

The standard screening test for high blood sugar in children with risk factors—a blood test called the fasting plasma (or blood) glucose test—identified nearly three times fewer children with prediabetes than did a longer blood test, said the study’s lead author.

"Prediabetes and metabolic syndrome are common in obese children but are not readily identified with the currently recommended test," said Katherine Morrison, MD, from the pediatrics department of McMaster University, Ontario, Canada. "They require a glucose stress test."

The authors studied 172 obese children, ages 5 to 17, who joined a program to help attain a healthy weight. All children had evaluation of risk factors for diabetes (or its precursor, prediabetes) and metabolic syndrome, including testing of blood sugar. Using the glucose stress test, researchers found 25% of the children met the diagnostic criteria for prediabetes.

When they relied on results of the fasting blood glucose test, as recommended by the American and Canadian diabetes associations, they found only 8% of the children had prediabetes.

Morrison said the more accurate test was the glucose stress test, also called the oral glucose-tolerance test. This test takes longer because the patient has blood drawn after fasting and again 2 hours after drinking a sugary solution.

Compared with the glucose stress test, the fasting-blood glucose test also was not as sensitive in detecting metabolic syndrome, which is a cluster of risk factors for heart disease and diabetes, including a high blood-sugar level.

"A large proportion of the children with prediabetes would not have had their condition recognized," Morrison said.

The same was true for the metabolic syndrome. Of the children in the study, 12.8% had a diagnosis of this syndrome (based on International Diabetes Federation pediatric criteria) using the glucose stress test, compared with 5.2% using the standard test, the authors reported.

Prediabetes and the metabolic syndrome usually cause no obvious symptoms. Early detection is important because changes in diet, regular exercise, and moderate weight loss can help prevent or delay diabetes and the metabolic syndrome. Although adults receive diabetes screening with either blood test, children typically do not get the 2-hour glucose stress test, Morrison said.

"The commonest reasons are the increased time, inconvenience, and cost required for 2-hour testing," she said. "But this research suggests that the recommended test for screening obese children for prediabetes and metabolic syndrome should be changed."

The study was funded by the Canadian Institutes for Health Research and the Heart and Stroke Foundation of Canada. The results were presented June 15 at the Endocrine Society‘s 90th annual meeting in San Francisco.

The organization conducts research on hormones and the clinical practice of endocrinology and counts as members more than14, 000 scientists, physicians, educators, nurses, and students worldwide.