Brian Hoyle

May 02, 2011

May 2, 2011 (Denver, Colorado) — The currently recommended blood test for glycated hemoglobin (HbA1C) can fail to detect type 2 diabetes in overweight children — missing the condition in more than two thirds of children at high risk. However, the addition of an oral glucose tolerance test (OGTT) can markedly improve the odds of catching type 2 diabetes in this population.

The results were presented here at the Pediatric Academic Societies and Asian Society for Pediatric Research 2011 Annual Meeting by Ghufran S. Babar, MD, a pediatric endocrinologist at Children's Mercy Hospital and Clinics, Kansas City, Missouri.

"Our research indicates that special consideration may need to be given to overweight children being tested for diabetes. Simply following the [American Diabetes Association] guidelines may not be enough to ensure that these children get proper care," Dr. Babar told Medscape Medical News.

The study was prompted by the 2010 revision by the American Diabetes Association of the clinical practice recommendations for type 2 diabetes screening. The revised recommendation dropped the previous gold standard of a 2 hour, 75 g OGTT, which measures the short-term metabolism of glucose after an overnight fast, in favor of the more convenient HbA1C test, which measures the average glucose level over several months (a value of 6.5% or higher is diagnostic of diabetes and confirms risk for retinopathy). HbA1c levels of 6.0% to 6.49% indicate a high risk of developing diabetes.

The retrospective study (2004 to 2008) examined the medical charts of 629 overweight children and adolescents who underwent both of the tests. On the basis of the OGTT data on glucose use, the patients were retrospectively categorized by the researchers as normal, impaired (high risk), or diabetic. The HbA1C results were then assessed.

Forty percent of patients categorized as diabetic and 67% of those categorized as impaired by the OGTT had normal HbA1c results. Furthermore, almost 9 of 10 of the patients (86%) displayed normal blood glucose levels on their HbA1c test.

The researchers concluded that the HbA1c test has a low sensitivity for diagnosing type 2 diabetes in overweight children and adolescents, and might delay the diagnosis of those at risk or in the early stage of type 2 diabetes.

"I wonder about a diagnosis based on OGTT. There have been studies indicating that OGTT results in an individual can vary over time," Katie Larson Ode, MD, from the division of pediatric endocrinology, University of Minneapolis Medical School, Minneapolis, told Medscape Medical News.

"I think both tests should be used in a high-risk population. HbA1c should not be the only test for diagnosis until further data are available," Dr. Babar told Medscape Medical News.

Dr. Babar and his colleagues speculate that, because of the nature of the HbA1c test, for some people in the early stage of type 2 diabetes and impaired glucose tolerance, the elevations in blood glucose might not be of sufficient duration or magnitude to result in a blood glucose level exceeding 6.5%.

"I think that it would be interesting to see if the authors could determine a threshold level of hemoglobin A1c between 5% and 6% that correlates with impairment of glucose tolerance, as determined by the 2-hour OGTT," Wayne Moore, MD, PhD, section chief of pediatric endocrinology at Children's Mercy Hospitals and Clinics, told Medscape Medical News. Dr. Moore was not affiliated with the study.

"We are planning to do further assessments of HBA1c while doing both the OGTT and HBA1c test at the same time on new-to-the-clinic patients who are showing clinical signs of insulin resistance and possible diabetes," Dr. Babar told Medscape Medical News.

Although the reinstitution of the OGTT would introduce an additional cost to patient examination and reintroduce the necessity of an overnight fast, it is worthwhile, according to Dr. Moore, "especially when one considers the cost of treating the chronic complications that result from undetected and untreated type 2 diabetes and impaired glucose tolerance."

"I have to think that these data give us reason to consider changing how we treat this patient population," session moderator Shari Barkin, chief of general pediatrics, Monroe Carrel Jr. Children's Hospital, Vanderbilt University, Nashville, Tennessee, told Medscape Medical News.

Dr. Babar has disclosed no relevant financial relationships.

Pediatric Academic Societies (PAS) and Asian Society for Pediatric Research 2011 Annual Meeting: Abstract 1635.1. Presented April 30, 2011.

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