Diagnosis of diabetes using hemoglobin A1c: should recommendations in adults be extrapolated to adolescents?

To compare test performance of hemoglobin A1c (HbA1c) for detecting diabetes mellitus/pre-diabetes for adolescents versus adults in the United States.

Individuals were defined as having diabetes mellitus (fasting plasma glucose [FPG] ≥ 126 mg/dL; 2-hour plasma glucose (2-hr PG) ≥ 200 mg/dL) or pre-diabetes (100 ≤ FPG < 126 mg/dL; 140 ≤ 2-hr PG < 200 mg/dL. HbA1c test performance was evaluated with receiver operator characteristic (ROC) analyses.

Few adolescents had undiagnosed diabetes mellitus (n = 4). When assessing FPG to detect diabetes, an HbA1c of 6.5% had sensitivity rates of 75.0% (30.1% to 95.4%) and 53.8% (47.4% to 60.0%) and specificity rates of 99.9% (99.5% to 100.0%) and 99.5% (99.3% to 99.6%) for adolescents and adults, respectively. Additionally, when assessing FPG to detect diabetes mellitus, an HbA1c of 5.7% had sensitivity rates of 5.0% (2.6% to 9.2%) and 23.1% (21.3% to 25.0%) and specificity rates of 98.3% (97.2% to 98.9%) and 91.1% (90.3% to 91.9%) for adolescents and adults, respectively. ROC analyses suggested that HbA1c is a poorer predictor of diabetes mellitus (area under the curve, 0.88 versus 0.93) and pre-diabetes (FPG area under the curve 0.61 versus 0.74) for adolescents compared with adults. Performance was poor regardless of whether FPG or 2-hr PG measurements were used.

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