HbA1c May Miss Diabetes in Adolescents

In comparison with results in adults with diabetes, hemoglobin A1c (HbA1c) testing in younger patients doesn’t have the same level of discrimination….

Dr. Joyce M. Lee and colleagues at University of Michigan, Ann Arbor stated that, “Given the poor performance of the HbA1c test in children, physicians who use HbA1c for diagnosis will likely miss cases of diabetes.”  

Dr. Lee observed that traditionally, for both adolescents and adults, a diagnosis of diabetes has been determined using a fasting plasma glucose (FPG) level or a 2-hour plasma glucose level after a 75-gram load of glucose.

However, the American Diabetes Association expert committee has favored phasing out these approaches and employing HbA1c. Nevertheless, the researchers say that it’s unclear whether similar HbA1c cutoff points are appropriate for the pediatric and the adult populations. The recommendations were made based on studies in adults.

To investigate, the team examined data on more than 1,400 patients aged 12 to 18 years (only four of whom had undiagnosed diabetes) and more than 8,200 aged 19 to 78 years for whom FPG or 2-hr PG results were available. Three hundred and thirty-one of the adults had undiagnosed diabetes.

When assessing FPG to detect diabetes, an HbA1c of 6.5% had sensitivity rate of 75.0% and a specificity rate of 99.9% in adolescents. Nevertheless, investigators point out that the 75% sensitivity estimate was highly unstable, with wide confidence intervals largely because of the few adolescents with diabetes.

Further analyses using receiver operator characteristics, say investigators, suggested that HbA1c is a poorer predictor of diabetes in adolescents than in adults. This was the case regardless of whether FPG or 2-hour plasma glucose measurements were used.

HbA1c was also a poor predictor of pre-diabetes for adolescents compared with adults.

The researchers suggest that alternative HbA1c thresholds to those used in adults may be useful for the pediatric population.

“Use of HbA1c for diagnosis of diabetes and pre-diabetes in adolescents may be premature until information from more definitive studies is available,” they conclude.