Blood Test for Predicting Childhood Diabetes Reconsidered

The glycosalated hemoglobin (HbA1c) blood test is a rapid and convenient way of diagnosing diabetes.

The HbA1c test has become the preferred way to diagnose diabetes among the millions of patients who have the disease, but are asymptomatic. The simple test measures longer-term blood sugar levels without requiring patients to fast overnight.

Scientists at the University of Michigan, (Ann Arbor, MI, USA), studied whether the assay could be used to make a diagnosis of diabetes mellitus in adolescents, using the standardized values for adults. For the study, they evaluated the testing results of 1,156 obese and overweight adolescents, aged 12-18 years. The American Diabetes Association, (Alexandria, VA, USA), recommends screening only obese and overweight children because their weight puts them at higher risk for developing diabetes.

Individuals were defined as having diabetes mellitus if their fasting plasma glucose (FPG) was equal to or greater than 126 mg/dL; a 2-hour plasma glucose (2-hr PG) equal to or greater than 200 mg/dL or were prediabetic where the FPG is between 100 and 126 mg/dL; and the 2-hr PG is between 140 and 200 mg/dL. According to the guidelines, individuals without symptoms would be classified as having diabetes if HbA1c values reach 6.5% and as having prediabetes if HbA1c values were between 6.0% and 6.4% on two separate tests.

Only four of the adolescents studied had undiagnosed diabetes mellitus. When assessing FPG to detect diabetes, an HbA1c of 6.5% had sensitivity rates of 75.0% for adolescents and 53.8% adults, although the specificity was higher. Additionally, when assessing FPG to detect diabetes mellitus, an HbA1c of 5.7% had sensitivity rates of 5.0% and 23.1%, and specificity rates of 98.3% and 91.1% for adolescents and adults, respectively. These analyses suggest that HbA1c is a poorer predictor of diabetes mellitus and prediabetes for adolescents compared with adults and performance was poor regardless of whether FPG or 2-hr PG measurements were used.

Joyce M. Lee, MD, MPH, a pediatric endocrinologist, and lead author of the study, said, "We found that hemoglobin A1c is not as reliable a test for identifying children with diabetes and prediabetes compared with adults and using this test in children may lead to missed cases." The study was published online ahead of print on December 30, 2010, in the Journal of Pediatrics.

Related Links:

University of Michigan

American Diabetes Association