Feb. 25, 2011 -- A simple blood test that measures long-term glucose levels -- the hemoglobin A1c (HbA1c) test -- may not be the best way to diagnose diabetes in adolescents.
The HbA1c screening test is easier to perform than the fasting plasma glucose test, which requires fasting for eight hours. But the new study, which appears in the Journal of Pediatrics, shows that the HbA1c test is less sensitive in diagnosing diabetes and prediabetes in children than in adults.
“My worry is that we could miss cases of diabetes,” says study researcher Joyce Lee, MD, a pediatric endocrinologist at University of Michigan’s Mott Children’s Hospital in Ann Arbor. “The HbA1c test just doesn’t perform as well in kids as it does in adults.”Lee says this test can be useful as an adjunct to other diabetes tests.
“You don’t want to rely on just this test to diagnose a child with diabetes,” she says. If a child is overweight and obese and has two of four risk factors for diabetes, they should be screened in some other way beside HbA1c.”
In the new study, researchers compared HbA1c screening results with those seen on fasting glucose tests among 1,156 obese and overweight adolescents aged 12 to 18. They compared these readings with those of 6,751 adults aged 19 to 79.
According to the American Diabetic Association guidelines, diabetes is diagnosed when an HbA1c level is 6.5% or more; prediabetes is diagnosed when an HbA1C level is between 6% and 6.4% on two separate tests. Prediabetes is marked by higher than normal glucose levels that places a person at risk for developing type 2 diabetes.
Using these cut-offs, the fasting test caught significantly more adolescents with diabetes and prediabetes than the HbA1c test, the study showed. The HbA1c was much more sensitive among adults than adolescents.
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