McMaster University

McMaster University

Faculty of
Health Sciences

Current screening test for prediabetes in children misses the diagnosis too often

Published: June 16, 2008
Katherine Morrison
Katherine Morrison, associate professor, pediatrics

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, says a McMaster 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 the children with prediabetes than did a longer blood test, said Katherine Morrison, associate professor, pediatrics, and the study’s lead author.

Morrison says 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 was also not as sensitive in detecting metabolic syndrome. This syndrome is a cluster of risk factors for heart disease and diabetes, including a high blood sugar level.

"Prediabetes and metabolic syndrome are common in obese children but are not readily identified with the currently recommended test," Morrison said. "They require a glucose stress test."

The study, presented today at The Endocrine Society’s annual meeting in San Francisco, 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, the researchers found that 25 percent of the children met the diagnostic criteria for prediabetes. But when they relied on results of the fasting blood glucose test, as recommended by the American and Canadian diabetes associations, they found that only eight percent of the children had prediabetes.

"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 percent had a diagnosis of this syndrome (based on International Diabetes Federation pediatric criteria) using the glucose stress test, compared with just 5.2 percent using the standard test.

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 two-hour glucose stress test, Morrison said.

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

Funding for the study was provided by the Canadian Institutes for Health Research and from the Heart and Stroke Foundation of Canada.

Dr. Michael Kramer, Scientific Director at the Canadian Institutes of Health Research, said, "Dr. Morrison and her colleagues have demonstrated that a full oral glucose tolerance test is more sensitive than a simple fasting blood sugar  test  in identifying obese children who are at increased risk of type 2 diabetes. These results should help parents and health care providers intervene earlier and hopefully prevent future cases of diabetes."

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