Obese children at risk of developing Type 2 diabetes may not be getting the news soon enough to take preventive action because the test used to gauge their condition is not sensitive enough, a new study suggests.

Researchers at McMaster University in Hamilton showed the standard test alone — called a fasting glucose test — missed two out of three children diagnosed as pre-diabetic by the fasting glucose test followed by a second test, a glucose stress test.

Under-diagnosing the problem means that kids and their families are missing an opportunity to make important lifestyle changes that have been shown to lower the risk of developing full-blown diabetes. Those changes are increasing exercise, losing weight and changing dietary habits.

"Really it is the recognition on both the part of the physician and to some extent on the part of the family that the child has experienced some negative metabolic effect from the obesity," lead author Dr. Katherine Morrison, a pediatric endocrinologist, said in an interview.

"Many parents don't think that kids can get health consequences. And so they don't think about them."

Morrison presented the findings Sunday to the annual meeting of the Endocrine Society in San Francisco.

She and her colleagues studied 172 obese children aged five to 17 who had joined a program to help them reach and maintain a healthy weight.

All children underwent evaluation for risk factors for diabetes or the precursor condition, pre-diabetes.

Fasting glucose test missed condition

When the children were tested using the fasting glucose test — which checks the blood for sugar levels after a fast — eight per cent were found to be pre-diabetic. But when the children went through the second test, the glucose stress test, 25 per cent met the criteria for pre-diabetes.

The American and Canadian diabetes associations recommend the fasting test only.

The stress test is a bit like cardiac stress tests, which check the heart's ability to cope with the rigours of exercise. In the glucose stress test, children who have fasted and been tested are then given a sugary liquid to drink and their blood sugar levels are again tested two hours later.

Morrison said the test shows whether the individual can process sugar normally or has impaired ability to metabolize it.

Until relatively recently, it was thought Type 2 diabetes was only a disease of later life — which is why it used to be called late onset diabetes. But it is now known that even adolescents can develop it. The condition contributes to heart disease, suggesting people who develop it early in life may face complications by mid-life.

In fact, Morrison said a longitudinal study that looked at cardiovascular risk factors in children who were then followed into adulthood found that those with multiple risk factors such as diabetes were at a vastly higher risk of having a heart attack by age 48 than other young adults.

"This tells us that the length of time that your body's exposed to these risk factors is also important in terms of developing heart disease down the road," she said.

"Clearly we have to become more aware of it. We've sort of always assumed this was an adult problem and we weren't going to think about it. But the research is telling us that perhaps we should be."

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