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HbA1c test may miss diabetes, prediabetes diagnoses in children
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Although accurate and convenient for detecting type 2 diabetes and prediabetes in adults, current HbA1c cutoffs may not be enough to diagnose diabetes in children.
A 2010 clinical practice guideline from the American Diabetes Association recommends that physicians exclusively use the HbA1c assay to detect diabetes. The guidelines recommend a cutoff of 6.5% or greater for diagnosis.
However, researchers for two recent studies highlight significant vulnerabilities in the recommended test’s ability to diagnose diabetes and prediabetes in children.
Emerging data
Joyce Lee, MD, MPH, and colleagues at CS Mott Children’s Hospital and the University of Michigan found sharp contrasts in the efficacy of the HbA1c assay for detecting type 2 diabetes in children vs. adults.
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The researchers evaluated the testing results of 1,156 overweight and obese adolescents aged 12 to 18 years. They compared the efficacy of detecting diabetes and prediabetes via fasting plasma glucose and 2-hour plasma glucose vs. various HbA1c cutoffs. When compared with FPG measurements of at least 126 mg/dL, a HbA1c cutoff of 6.5% yielded a 75% sensitivity for diagnosing type 2 diabetes. Lowering the cutoff to 5.7% yielded an even lower sensitivity of 5%.
“Our study provided evidence that the HbA1c test doesn’t work as well in kids as it does in adults,” Lee told Endocrine Today.
The ADA recommends screening only obese and overweight children because their weight puts them at a higher risk for developing diabetes. 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 reach between 6% and 6.4% on two separate tests. These results suggest that the cutoff point may need to be even lower for children, the researchers said.
“Recommendations may need to be reconsidered for children,” Lee said.
Two tests better than one?
A study conducted by researchers at Children’s Mercy Hospital in Kansas City, Mo., found that using the HbA1c test alone missed more than two-thirds of children at high-risk for type 2 diabetes. However, using two tests — the HbA1c and the oral glucose tolerance test — dramatically reduced the risk for delayed diagnosis in overweight children.
Results of a retrospective chart review of 629 overweight children and adolescents who had both tests were presented at the 2011 Pediatric Academic Societies Annual Meeting. Data show that 40% of adolescents with type 2 diabetes and 67% of adolescents at high-risk for diabetes using the OGTT would have shown a normal glycemic status if only the HbA1c test was used for diagnosis. In addition, nearly nine of 10 patients (86%) had normal glucose levels according to their HbA1c results.
“Our research indicates that special consideration may need to be given to overweight children being tested for diabetes,” Ghufran S. Babar, MD, a pediatric endocrinologist at Children’s Mercy Hospital, said in a press release. “Simply following the guidelines may not be enough to ensure these children get proper care.”
Determining the optimal test
While the HbA1c may be a useful tool to try to identify children with diabetes, Lee said she disagrees with exclusive use in the clinical setting. Its use in children is further complicated, coupled with the fact that HbA1c levels rise with age and differ among races/ethnicities, making broad cut-points debatable.
“Glucose measurements still have a very important role, and I don’t think those can be discounted, but I would suggest that if a clinician is going to use HbA1c he or she should use a FPG or 2-hour OGTT as well,” she said in the interview.
Babar expressed similar sentiments, noting that combining the two tests may produce accurate results compared with HbA1c alone. – by Melissa Foster
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Disclosure: Drs. Babar and Lee report no relevant financial disclosures.
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