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HbA1C may miss diabetes in adolescents

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – In comparison with results in adults with diabetes, hemoglobin A1c (HbA1C) testing in younger patients doesn’t have the same level of discrimination, researchers report in a January 3rd on-line paper in the Journal of Pediatrics.

“Given the poor performance of the HbA1c test in children, physicians who use HbA1c for diagnosis will likely miss cases of diabetes.” Dr. Joyce M. Lee told Reuters Health by email.

Dr. Lee and colleagues at University of Michigan, Ann Arbor observe that traditionally, for both adolescents and adults, a diagnosis of diabetes mellitus 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 1400 patients aged 12 to 18 years (only 4 of whom had undiagnosed diabetes) and more than 8200 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. Corresponding values in adults were 53.8% and 99.5%. Nevertheless, investigators point out that the 75% sensitivity estimate was highly unstable, with wide confidence intervals largely because of the few adolescents with diabetes.

When an HbA1C of 5.7% was employed, the rates were 5% and 98.3% in adolescents and 23.1% and 93.1% in adults.

Further analyses using receiver operator characteristics, say investigators, suggested that HbA1c is a poorer predictor of diabetes mellitus 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 mellitus and pre-diabetes in adolescents may be premature until information from more definitive studies is available.” they conclude.


Diagnosis of Diabetes using Hemoglobin A1c: Should Recommendations in Adults Be Extrapolated to Adolescents?

J Pediatr 2011.